Update to Gutenberg v1.63.0 tag

[guarani]

This is a follow-up to #17249 and all it does is update the Gutenberg Mobile reference from a commit to a tag, v1.63.0.

To test:

Make sure CI checks are green.

Regression Notes

1. Potential unintended areas of impact

Since this touches the Gutenberg Mobile integration, anything in Gutenberg Mobile.

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

I verified that the tag points to the same exact commit previously pointed to.

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

No automated tests added b/c this is a Gutenberg Mobile Iintegration PR.

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]

You can trigger an installable build for these changes by visiting CircleCI here.

[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

Generated by 🚫 dangerJS

[mokagio]

Thank you and sorry for requiring you to make a new PR because of my haphazard merge of the previous PR.

[guarani]

Not at all, thanks for all the great work wrangling the WPiOS releases! ❤️