Jetpack Social: Hide Jetpack Social for private posts

[wargcm]

Fixes #21290

Description

Hides Jetpack social when the post is private in the pre-publishing sheet and post settings screen.

Testing

To test:

• Launch Jetpack and login
• Select a blog with no social connections
• Create a new post
• Open the Post Settings screen (... > Post Settings)
• 🔍 Verify the no social connections view is shown
• Tap on Visibility
• Select Private
• 🔍 Verify the no social connections view is not shown
• Navigate back to the post
• Type something in to enable the Publish button and tap on it
• 🔍 Verify the no social connections view is not shown
• Tap on Visibility
• Select Public
• 🔍 Verify the no social connections view is shown
• Discard the post
• Switch to a blog which has social connections or set one up
• Repeat the above steps but verify with the social sharing views

Regression Notes

1. Potential unintended areas of impact
   N/A

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)
   N/A

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 WordPress Alpha by scanning the QR code below to install the corresponding build.

	App Name	WordPress Alpha
	Configuration	Release-Alpha
	Build Number	pr21362-12a3aa7
	Version	23.0
	Bundle ID	org.wordpress.alpha
	Commit	12a3aa7
	App Center Build	WPiOS - One-Offs #6755

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 Jetpack Alpha by scanning the QR code below to install the corresponding build.

	App Name	Jetpack Alpha
	Configuration	Release-Alpha
	Build Number	pr21362-12a3aa7
	Version	23.0
	Bundle ID	com.jetpack.alpha
	Commit	12a3aa7
	App Center Build	jetpack-installable-builds #5791

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

[dvdchr]

Verified that the Jetpack Social section is no longer shown for private posts. LGTM!

FYI: I've updated the base branch to release/23.1 since it's a pretty small change.

[wargcm]

Thanks @dvdchr!