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

See #32246.


git-svn-id: https://develop.svn.wordpress.org/trunk@32340 602fd350-edb4-49c9-b593-d223f7449a82

src/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);