Improve help message of VideoPress Privacy Setting at the block level.

[pgk]

Based on this comment by @pablohoneyhoney

The text below the privacy selector could be dynamic and contextual to the selected privacy setting. The default state shall ideally be instructional of the interaction and also tell you what the site setting is currently.

Fixes #

Changes proposed in this Pull Request:

Jetpack product discussion

pxWta-1kj-p2#comment-5651

Testing instructions:

• On your Jetpack site with VideoPress enabled, create a new post and add a new Video
• Select the VideoPress block and change the privacy setting. The help messages change accordingly.

Does this pull request change what data or activity we track or use?

no

[matticbot]

Caution: This PR has changes that must be merged to WordPress.com
Hello pgk! These changes need to be synced to WordPress.com - If you 're an a11n, please commandeer and confirm D79810-code works as expected before merging this PR. Once this PR is merged, please commit the changes to WP.com. Thank you!
This revision will be updated with each commit to this PR

[github-actions]

Thank you for your PR!

When contributing to Jetpack, we have a few suggestions that can help us test and review your patch:

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• ✅ Add testing instructions.
  
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• ✅ Add changelog entries to affected projects
  

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Jetpack plugin:

• Next scheduled release: June 7, 2022.
• Scheduled code freeze: May 31, 2022.

[thedebian]

Worked well 👍

[github-actions]

Great news! One last step: head over to your WordPress.com diff, D79810-code, and deploy it.
Once you've done so, come back to this PR and add a comment with your changeset ID.

Thank you!

[pgk]

r245278-wpcom