Fires immediately after deleting metadata of a specific type.
The dynamic portion of the hook,
$meta_type, refers to the meta object type
(post, comment, term, user, or any other type with an associated meta table).
Possible hook names include:
Related Functions: delete_site_meta, delete_metadata, delete_post_meta_by_key, delete_meta, delete_theme, delete_site_meta_by_key