Bump actions/checkout from 2 to 4

Bumps [actions/checkout](https://github.com/actions/checkout) from 2 to 4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v2...v4)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

.github/workflows/docs.yml

@@ -38,7 +38,7 @@ jobs:
     steps:
       # Checks-out your repository under $GITHUB_WORKSPACE
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
         with:
           # Need to fetch more than the last commit so that setuptools-scm can
           # create the correct version string. If the number of commits since
@@ -118,7 +118,7 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
 
       # Fetch the built docs from the "build" job
       - name: Download HTML documentation artifact
@@ -128,7 +128,7 @@ jobs:
           path: doc/_build/html
 
       - name: Checkout the gh-pages branch in a separate folder
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
         with:
           ref: gh-pages
           # Checkout to this folder instead of the current one

.github/workflows/pypi.yml

@@ -31,7 +31,7 @@ jobs:
     steps:
       # Checks-out your repository under $GITHUB_WORKSPACE
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
         with:
           # Need to fetch more than the last commit so that setuptools_scm can
           # create the correct version string. If the number of commits since
@@ -98,7 +98,7 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
         with:
           # The GitHub token is preserved by default but this job doesn't need
           # to be able to push to GitHub.

.github/workflows/style.yml

@@ -20,7 +20,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
         with:
           persist-credentials: false
 
@@ -42,7 +42,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
         with:
           persist-credentials: false
 

.github/workflows/test.yml

@@ -62,7 +62,7 @@ jobs:
 
       # Checks-out your repository under $GITHUB_WORKSPACE
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
         with:
           # Need to fetch more than the last commit so that setuptools_scm can
           # create the correct version string. If the number of commits since