[10.x] Incorrect return in FileSystem.php (#50459)

* [10.x] incorrect return

* Update Filesystem.php

---------

Co-authored-by: Taylor Otwell <taylor@laravel.com>

src/Illuminate/Filesystem/Filesystem.php

@@ -347,7 +347,7 @@ public function copy($path, $target)
      *
      * @param  string  $target
      * @param  string  $link
-     * @return void
+     * @return bool|null
      */
     public function link($target, $link)
     {