Fix blockGap output for block style variations.

[tellthemachines]

Trac ticket: https://core.trac.wordpress.org/ticket/64533

Changes from WordPress/gutenberg#74529.

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This Pull Request is for code review only. Please keep all other discussion in the Trac ticket. Do not merge this Pull Request. See GitHub Pull Requests for Code Review in the Core Handbook for more details.

[tellthemachines]

PROTECTED_PROPERTIES should be removed altogether because it's not used anymore. I'm not sure if it's OK to remove outright - as I'm doing in WordPress/gutenberg#74529 - or if there's a way to deprecate it or something. In case some third party is extending the class and for some reason using that const?

[github-actions]

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[github-actions]

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[aaronrobertshaw]

Thanks for putting this together @tellthemachines 👍

✅ The changes match both WordPress/gutenberg#74529 & WordPress/gutenberg#75038
✅ New unit test looks good (thanks)

There was only one tiny issue I spotted and left a note on below but assuming that is tweaked, this LGTM!

🚢

[github-actions]

A commit was made that fixes the Trac ticket referenced in the description of this pull request.

SVN changeset: 61564
GitHub commit: e3ad7a0

This PR will be closed, but please confirm the accuracy of this and reopen if there is more work to be done.