Remove sendReceiptAfterPayment and tapToPayEducation feature flags

[staskus]

Description

• Remove sendReceiptAfterPayment and tapToPayEducation feature flags
• Remove backendReceips feature flag - it has been enabled for a long time
• Remove no longer needed code with AboutTapToPayView, make renamings / replace with TapToPayEducationView

Steps to reproduce

The only meaningful change is replacing AboutTapToPayView with TapToPayEducationView in two places:

• Set Up Tap to Pay view
• Set Up Tap to Pay complete view

1. Open Menu
2. Payments
3. Tap 'Set Up Tap to Pay on iPhone'
4. Tap 'Learn More' at the bottom
5. Confirm education is opened
6. Finish education by tapping 'Set Up Tap to Pay on iPhone'
7. Confirm set up flow starts
8. Complete the flow
9. Confirm 'Setp complete' opens
10. Tap 'Learn More' at the bottom
11. Confirm education is opened

Testing information

Tested Tap to Pay and email flow on iPhone 14 Pro 17.7

Screenshots

Education.MP4

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• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

Reviewer (or Author, in the case of optional code reviews):

Please make sure these conditions are met before approving the PR, or request changes if the PR needs improvement:

• The PR is small and has a clear, single focus, or a valid explanation is provided in the description. If needed, please request to split it into smaller PRs.
• Ensure Adequate Unit Test Coverage: The changes are reasonably covered by unit tests or an explanation is provided in the PR description.
• Manual Testing: The author listed all the tests they ran, including smoke tests when needed (e.g., for refactorings). The reviewer confirmed that the PR works as expected on all devices (phone/tablet) and no regressions are added.

[dangermattic]

	1 Warning
⚠️	This PR is larger than 300 lines of changes. Please consider splitting it into smaller PRs for easier and faster reviews.

Generated by 🚫 Danger

[wpmobilebot]

📲 You can test the changes from this Pull Request in WooCommerce iOS by scanning the QR code below to install the corresponding build.

	App Name	WooCommerce iOS
	Build Number	pr14963-98bec1e
	Version	21.5
	Bundle ID	com.automattic.alpha.woocommerce
	Commit	98bec1e
	App Center Build	WooCommerce - Prototype Builds #12710

Automatticians: You can use our internal self-serve MC tool to give yourself access to App Center if needed.

[wpmobilebot]

Version 21.5 has now entered code-freeze, so the milestone of this PR has been updated to 21.6.

[iamgabrielma]

LGTM

PD: My physical device is pretty much like yours, tested w iPhone 14 on iOS 17.7.1. Any potential concern from iOS18?

[staskus]

PD: My physical device is pretty much like yours, tested w iPhone 14 on iOS 17.7.1. Any potential concern from iOS18?

Good question. The low likelihood concern is updated transitions from AboutView to TapToPayEducation sheets. Sometimes they do break when something changes between iOS versions. I will test it on a simulator.