Add a missing @return tag to the DocBlock for `uninstall_plugin().

See #32246.

Built from https://develop.svn.wordpress.org/trunk@32340


git-svn-id: http://core.svn.wordpress.org/trunk@32311 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/includes/plugin.php

@@ -944,6 +944,7 @@ function is_uninstallable_plugin($plugin) {
  * @since 2.7.0
  *
  * @param string $plugin Relative plugin path from Plugin Directory.
+ * @return true True if a plugin's uninstall.php file has been found and included.
  */
 function uninstall_plugin($plugin) {
 	$file = plugin_basename($plugin);