Description

When adding a new block, sometimes you have to save changes twice to clear unsaved changes.

Step-by-step reproduction instructions

1. Go to the new widgets screen.
2. Add a new block to a widget area.
3. Save changes.
4. See snackbar appear.
5. "Update" button isn't disabled.

Expected behaviour

The "Update" button should be disabled after saving changes the first time.

Actual behaviour

Have to save changes twice to see a visual indication that they are saved.

Screenshots or screen recording (optional)

WordPress information

• WordPress version: 5.7.2
• Gutenberg version: 10.7/trunk
• Are all plugins except Gutenberg deactivated? Yes
• Are you using a default theme (e.g. Twenty Twenty-One)? Yes