Integrate gutenberg-mobile release 1.56.0

[geriux]

Description

This PR incorporates the 1.56.0 release of gutenberg-mobile.
For more information about this release and testing instructions, please see the related Gutenberg-Mobile PR: wordpress-mobile/gutenberg-mobile#3664

Release Submission Checklist

• 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 test the changes on this Pull Request by downloading it from AppCenter here with build number: 51447. IPA is available here. If you need access to this, you can ask a maintainer to add you.

[peril-wordpress-mobile]

You can trigger optional UI/connected tests for these changes by visiting CircleCI here.

[SiobhyB]

LGTM! 🎉 I tested on an iPhone XR (iOS 14.4) to verify that the editor doesn't crash. I covered the following in my testing:

• Edited an existing post and published a new one.
• Edited an existing page and published a new one.
• Inserted and modified some blocks at random.

I also verified that the following changes are in place and work as expected:

• New block: Layout grid.
• Tablet view fixes for inserter button. (I verified that there are no unintended side effects to the inserter on my iPhone.)

(The other changes being introduced with this release are specific to Android.)