Propagate $useMasterKey to ParseFile when saving ParseObject

Author: zeliard91

src/Parse/ParseObject.php

@@ -987,7 +987,7 @@ private static function deepSave($target, $useMasterKey = false)
         }
 
         foreach ($unsavedFiles as &$file) {
-            $file->save();
+            $file->save($useMasterKey);
         }
 
         $objects = [];