By adding the `$output` parameter to `get_attachment_taxonomies()`, the function signature matches that of `get_object_taxonomies()`. The change also allows for more consistent behavior when passing `output=objects` to `get_object_taxonomies()` for the 'attachment' object type, since the `$output` parameter is now passed through the function stack. Props codemovement.pk. See #37368. git-svn-id: https://develop.svn.wordpress.org/trunk@38292 602fd350-edb4-49c9-b593-d223f7449a82