Description

If you export a synced pattern the sync type (synced/unsynced) is not stored in the json file.
So an imported unsynced pattern will always become a synced pattern after import and the user has no way to change that to unsynced.

Step-by-step reproduction instructions

1. Go to /wp-admin/edit.php?post_type=wp_block
2. Export a synced pattern
3. Permanently delete the pattern you just exported
4. Import the pattern and notice it now is marked as fully synced and you cannot change that

Screenshots, screen recording, code snippet

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Environment info

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Please confirm that you have searched existing issues in the repo.

Yes

Please confirm that you have tested with all plugins deactivated except Gutenberg.

Yes