Update Editor Publish button tint color from editorPrimary to UIColor.black

[derekblank]

To test:

1. Open a page or post
2. Type text into post header and post content
3. Note that Publish button has changed from blue (.editorPrimary) to UIColor.black

Regression Notes

1. Potential unintended areas of impact
   None.

2. What I did to test those areas of impact (or what existing automated tests I relied on)
   N/A

3. What automated tests I added (or what prevented me from doing so)
   TBD

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.

UI Changes testing checklist:

• Portrait and landscape orientations.
• Light and dark modes.
• Fonts: Larger, smaller and bold text.
• High contrast.
• VoiceOver.
• Languages with large words or with letters/accents not frequently used in English.
• Right-to-left languages. (Even if translation isn’t complete, formatting should still respect the right-to-left layout)
• iPhone and iPad.
• Multi-tasking: Split view and Slide over. (iPad)

[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	pr20951-1818a3e
	Version	22.5
	Bundle ID	com.jetpack.alpha
	Commit	1818a3e
	App Center Build	jetpack-installable-builds #5165

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

[wpmobilebot]

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

	App Name	WordPress Alpha
	Configuration	Release-Alpha
	Build Number	pr20951-1818a3e
	Version	22.5
	Bundle ID	org.wordpress.alpha
	Commit	1818a3e
	App Center Build	WPiOS - One-Offs #6138

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

[derekblank]

Closing, fixed in #20930.