Media: Fix the documented return type of the wp_update_attachment_metadata() function.

Props justlevine

See #63268

git-svn-id: https://develop.svn.wordpress.org/trunk@60300 602fd350-edb4-49c9-b593-d223f7449a82

Author: johnbillion

src/wp-includes/post.php

@@ -6877,7 +6877,9 @@ function wp_get_attachment_metadata( $attachment_id = 0, $unfiltered = false ) {
  *
  * @param int   $attachment_id Attachment post ID.
  * @param array $data          Attachment meta data.
- * @return int|false False if $post is invalid.
+ * @return int|bool Whether the metadata was successfully updated.
+ *                  True on success, the Meta ID if the key didn't exist.
+ *                  False if $post is invalid, on failure, or if $data is the same as the existing metadata.
  */
 function wp_update_attachment_metadata( $attachment_id, $data ) {
 	$attachment_id = (int) $attachment_id;