Gutenlypso: Autosave loops when triggered after publishing a post.

[kwight]

When editing a published Gutenberg post, autosave will loop endlessly every few seconds once an edit triggers it.

Steps to reproduce

1. Starting at URL: https://wpcalypso.wordpress.com/block-editor/post/
2. Create and publish a post.
3. Trigger another autosave by making an edit.
4. Observe looping autosave calls in devtools.

[kwight]

This appears to be a core Gutenberg regression (autosaves should only fire if there have been changes since the last autosave: WordPress/gutenberg#12318