Describe the bug
The "Two buttons" pattern triggers a validation error with 5.8 RC1. It looks like the pattern is using old markup - WordPress/gutenberg#21923.

To Reproduce
Steps to reproduce the behavior:

1. Update to WP 5.8 RC1
2. Create or edit a post.
3. See validation errors in the console.

Expected behavior
Core patterns shouldn't trigger validation errors.

Screenshots