Add array return type to all hook_removed_post_updates implementations

Changes makes sense, had a few extra hits wehen looking around for missed ones. But those hits were in

system.install

Seems to cover all bases :) Nice one.

Applied the diff and get one more

$ grep "Function .*_removed_post_updates\\\\.* has no return type specified" core/.phpstan-baseline.php
        'message' => '#^Function test_theme_depending_on_modules_removed_post_updates\\(\\) has no return type specified\\.$#',

Ah, the phpdoc comment didn't match the right format, so my find command didn't find it. Have rebased, updated, and fixed the docs at the same time.

Feedback appears to be addressed on this one.

Committed/pushed to 11.x and cherry-picked to 11.1.x thanks!

catch → closed merge request !9927

Retroactively crediting @mstrelan for all the work (issue, automation + MR), and @bbrala for the review.

Automatically closed - issue fixed for 2 weeks with no activity.