Real-time collaboration: Skip autosave modal to be overridden when collaborative-editing is enabled

[pkevan]

What?

Pulled from: #72040, this allows the autosave modal to be removed when sync is enabled.

Why?

To avoid interrupting the collaborative editing experience, we want to remove the modal from appearing.

How?

Checks that the post type has collaborative-editing enabled via post_type_supports and disabled the autosave modal.

Testing Instructions

1. Check out this branch.
2. Enable the real-time collaboration experiment: Gutenberg > Experiments.
3. Open a post or page for editing in two different browser environments.
4. Use your browser's development tools to remove the post editor lock.
5. Observe that no autosave modal appears.

[github-actions]

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[github-actions]

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