[Site Design Revamp] Update recommended designs caption font

[twstokes]

Fixes #18674

• Reduces the font size from Subhead / Semibold to Footnote / Regular [HIG typography]
• Reduces the margin between the title and the caption

Before	After

Testing

1. Start the Site Creation flow
2. Navigate to the Site Design picker screen
3. Observe the font size of the caption for the recommended designs section

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)

• None

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

• This was purely visual.

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.

[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 pr18786-fa59efa 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 pr18786-fa59efa on your iPhone

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

[antonis]

Great work @twstokes 👍
I've tested the CI build on an iPhone SE 2020 (iOS 14.7.1) and it works as expected. The code changes also LGTM 🎉