[core] Yaml format match most common convention

.github/ISSUE_TEMPLATE/1.bug.yml

@@ -8,7 +8,6 @@ body:
         Please provide a searchable summary of the issue in the title above ⬆️.
 
         Thanks for contributing by creating an issue! ❤️
-
   - type: input
     attributes:
       label: Search keywords
@@ -23,12 +22,12 @@ body:
       options:
         - label: I have tested the latest version
           required: true
-
   - type: textarea
     attributes:
       label: Steps to reproduce
       description: |
-        **⚠️ Please provide a live example for your report⚠️**
+        **⚠️ Issues that we can't reproduce can't be fixed.**
+
         If you don't have one, you can use one of these options:
           - [DataGrid codesandbox template](https://codesandbox.io/s/github/mui/mui-x/tree/master/templates/x-data-grid?file=/src/demo.tsx)
           - Fork any of the examples in our [documentation](https://mui.com/x/introduction/) by [clicking on the codesandbox or stackblitz icon](https://mui.com/static/docs/forking-an-example.png)

.github/ISSUE_TEMPLATE/2.feature.yml

@@ -8,7 +8,6 @@ body:
         Please provide a searchable summary of the issue in the title above ⬆️.
 
         Thanks for contributing by creating an issue! ❤️
-
   - type: input
     attributes:
       label: Search keywords
@@ -23,7 +22,6 @@ body:
       options:
         - label: I have tested the latest version
           required: true
-
   - type: textarea
     attributes:
       label: Summary 💡

.github/ISSUE_TEMPLATE/3.pro-support.yml

@@ -9,7 +9,6 @@ body:
         Please provide a searchable summary of the issue in the title above ⬆️.
 
         ⚠️ **Don't use this form if the problem is [a bug](https://github.com/mui/mui-x/issues/new?assignees=&labels=status%3A+needs+triage&template=1.bug.yml) or a [feature request](https://github.com/mui/mui-x/issues/new?assignees=&labels=status%3A+needs+triage&template=2.feature.yml), use the dedicated form instead.**
-
   - type: input
     id: contact
     attributes:
@@ -18,7 +17,6 @@ body:
       placeholder: 'e.g. 11111'
     validations:
       required: true
-
   - type: input
     attributes:
       label: Search keywords
@@ -33,7 +31,6 @@ body:
       options:
         - label: I have tested the latest version
           required: true
-
   - type: textarea
     attributes:
       label: The problem in depth 🔍

.github/ISSUE_TEMPLATE/4.premium-support.yml

@@ -9,7 +9,6 @@ body:
         Please provide a searchable summary of the issue in the title above ⬆️.
 
         ⚠️ **Don't use this form if the problem is [a bug](https://github.com/mui/mui-x/issues/new?assignees=&labels=status%3A+needs+triage&template=1.bug.yml) or a [feature request](https://github.com/mui/mui-x/issues/new?assignees=&labels=status%3A+needs+triage&template=2.feature.yml), use the dedicated form instead.**
-
   - type: input
     id: contact
     attributes:
@@ -18,7 +17,6 @@ body:
       placeholder: 'e.g. 11111'
     validations:
       required: true
-
   - type: input
     attributes:
       label: Search keywords
@@ -33,7 +31,6 @@ body:
       options:
         - label: I have tested the latest version
           required: true
-
   - type: textarea
     attributes:
       label: The problem in depth 🔍

.github/ISSUE_TEMPLATE/5.priority-support.yml

@@ -7,7 +7,6 @@ body:
     attributes:
       value: |
         Please provide a searchable summary of the issue in the title above ⬆️.
-
   - type: input
     attributes:
       label: Search keywords
@@ -22,7 +21,6 @@ body:
       options:
         - label: I have tested the latest version
           required: true
-
   - type: textarea
     attributes:
       label: The problem in depth 🔍

.github/ISSUE_TEMPLATE/6.docs-feedback.yml

@@ -9,15 +9,13 @@ body:
         Please provide a searchable summary of the issue in the title above ⬆️.
 
         Thanks for contributing by creating an issue! ❤️
-
   - type: input
     attributes:
       label: Search keywords
       description: Your issue may have already been reported! List the keywords you've used to search the [existing issues](https://github.com/mui/mui-x/issues). This will also make your issue searchable for others.
       placeholder: e.g. datagrid column resizing
     validations:
       required: true
-
   - type: input
     id: page-url
     attributes:
@@ -26,7 +24,6 @@ body:
       placeholder: https://mui.com/x/
     validations:
       required: true
-
   - type: dropdown
     attributes:
       label: Kind of issue
@@ -38,15 +35,13 @@ body:
         - Other
     validations:
       required: true
-
   - type: textarea
     attributes:
       label: Issue description
       description: |
         Let us know what went wrong when you were using this documentation and what we could do to improve it.
       value: |
         I was looking for ... and it appears that ...
-
   - type: textarea
     attributes:
       label: Context 🔦

.github/ISSUE_TEMPLATE/7.rfc.yml

@@ -13,18 +13,15 @@ body:
     attributes:
       label: What's the problem? 🤔
       description: Write a short paragraph or bulleted list to briefly explain what you're trying to do, what outcomes you're aiming for, and any other relevant details to help us understand the motivation behind this RFC.
-
   - type: textarea
     attributes:
       label: What are the requirements? ❓
       description: Provide a list of requirements that should be met by the accepted proposal.
-
   - type: textarea
     attributes:
       label: What are our options? 💡
       description: |
         Have you considered alternative options for achieving your desired outcome? It's not necessary to go into too much detail here, but it can help strengthen your main proposal.
-
   - type: textarea
     attributes:
       label: Proposed solution 🟢
@@ -35,7 +32,6 @@ body:
         - using diagrams to help illustrate your ideas
         - including code examples if you're proposing an interface or system contract
         - linking to relevant project briefs or wireframes
-
   - type: textarea
     attributes:
       label: Resources and benchmarks 🔗