Jetpack Social: Update release notes

[momo-ozawa]

Description

• Added release notes for Jetpack Social: Update the jetpack social sharing #19262

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.

[peril-wordpress-mobile]

	Warnings
⚠️	This PR is assigned to a milestone which is closing in less than 4 days Please, make sure to get it merged by then or assign it to a later expiring milestone
⚠️	This PR contains changes to RELEASE_NOTES.txt. Note that these changes won't affect the final version of the release notes as this version is in code freeze. Please, get in touch with a release manager if you want to update the final release notes.

Generated by 🚫 dangerJS

[wpmobilebot]

You can test the changes in Jetpack from this Pull Request by:

• Clicking here or scanning the QR code below to access App Center
• Then installing the build number pr19285-9c0f6f4 on your iPhone

If you need access to App Center, please ask a maintainer to add you.

[wpmobilebot]

You can test the changes in WordPress from this Pull Request by:

• Clicking here or scanning the QR code below to access App Center
• Then installing the build number pr19285-9c0f6f4 on your iPhone

If you need access to App Center, please ask a maintainer to add you.

[enejb]

Thanks for your help here @momo-ozawa

[mokagio]

Thanks @momo-ozawa !