Gallery Blocks are now marked as invalid block content

[skorasaurus]

Not sure if anyone reads this anymore; but some of the gallery blocks (not all) now display as invalid block content in the block editor.

I understand this is a gutenberg error likely (improperly migrating old, deprecating block markup/attributes) ; but new gallery blocks with new gallery block markup should also be used.

To reproduce:

1. activate plugin
2. visit the draft page of the block-unit-test
3. search for Three Column, Four Images in the browser

Tested:
WordPress 5.9.1
Gutenberg 12.7.1