Drop iOS 14 Support: Address UIButton API deprecations (#3)

[kean]

Related Issue #20860

Remove some unused code with UIButton deprecations.

Test Test

• Tap the "Create New" FAB on dashboard
• Verify that buttons are displayed correctly

I verified it with an image diff tool. The new API works the same with the only exception how the dynamic type works: it leaves slightly less space between buttons, which I think is an improvement.

before → after

Regression Notes

1. Potential unintended areas of impact: Media-related features
2. What I did to test those areas of impact (or what existing automated tests I relied on): manual tests and unit tests
3. What automated tests I added (or what prevented me from doing so): yes

PR submission checklist:

• I have completed the Regression Notes.
• I have considered adding unit tests for my changes.
• I have considered adding accessibility improvements for my changes.
• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

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	Build Number	pr21023-d7dd958
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	Commit	d7dd958
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[wpmobilebot]

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

	App Name	Jetpack Alpha
	Configuration	Release-Alpha
	Build Number	pr21023-d7dd958
	Version	22.7
	Bundle ID	com.jetpack.alpha
	Commit	d7dd958
	App Center Build	jetpack-installable-builds #5268

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