wp-includes/post.php:2829Unregisters a meta key for posts.
$post_typestring$meta_keystringboolfunction unregister_post_meta( $post_type, $meta_key ) { return unregister_meta_key( 'post', $meta_key, $post_type );}Introduced in 4.9.8. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/post.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.