delete_post_meta_by_key() is currently broken

[Viper007Bond]

$wpdb->prepare() quotes strings and therefore results in a broken query:

$wpdb->query( $wpdb->prepare("DELETE FROM $wpdb->postmeta WHERE meta_id IN(%s)", implode( ',', $postmetaids) ) );

It results in something like this:

DELETE FROM wp_postmeta WHERE meta_id IN('883,1062,1063,1064,1066,1067,969')

There are likely other places where this is also an issue.

Don't use prepare()

Props to DD32 by the way for pointing out to me what was going wrong.

I have added some testcases to wordpress-tests to catch this error.

I would prefer to keep the call to prepare here for consistency sake.

Going to commit an alternative fix which works for my local tests please re-open if there are still issues.

(In [12156]) Fix delete_post_meta_by_key() so that you can delete postmeta items by key again. Fixes #11100.