Add missing doc blocks to wp-admin/includes/*.

Fix some egregious uses of tabbing.
Some functions can simply return `apply_filters(...)` instead of setting a variable that is immediately returned.

See #32444.


git-svn-id: https://develop.svn.wordpress.org/trunk@32654 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/includes/theme.php

@@ -15,7 +15,7 @@
  *
  * @param string $stylesheet Stylesheet of the theme to delete
  * @param string $redirect Redirect to page when complete.
- * @return mixed
+ * @return void|bool|WP_Error When void, echoes content.
  */
 function delete_theme($stylesheet, $redirect = '') {
 	global $wp_filesystem;
@@ -123,7 +123,7 @@ function _get_template_edit_filename($fullpath, $containingfolder) {
  * @since 2.7.0
  * @see get_theme_update_available()
  *
- * @param object $theme Theme data object.
+ * @param WP_Theme $theme Theme data object.
  */
 function theme_update_available( $theme ) {
 	echo get_theme_update_available( $theme );