Docs: Correct @return value for update_attached_file().

Follow-up to [4612], [21967], [24490], [47611], [48214].

Props arnoutblueshell, karthickmurugan, SergeyBiryukov.
Fixes #62803.

git-svn-id: https://develop.svn.wordpress.org/trunk@59602 602fd350-edb4-49c9-b593-d223f7449a82

Author: SergeyBiryukov

src/wp-includes/post.php

@@ -852,13 +852,15 @@ function get_attached_file( $attachment_id, $unfiltered = false ) {
  * Updates attachment file path based on attachment ID.
  *
  * Used to update the file path of the attachment, which uses post meta name
- * '_wp_attached_file' to store the path of the attachment.
+ * `_wp_attached_file` to store the path of the attachment.
  *
  * @since 2.1.0
  *
  * @param int    $attachment_id Attachment ID.
  * @param string $file          File path for the attachment.
- * @return bool True on success, false on failure.
+ * @return int|bool Meta ID if the `_wp_attached_file` key didn't exist for the attachment.
+ *                  True on successful update, false on failure or if the `$file` value passed
+ *                  to the function is the same as the one that is already in the database.
  */
 function update_attached_file( $attachment_id, $file ) {
 	if ( ! get_post( $attachment_id ) ) {