fix test

Author: stas17

test/Gitlab/Tests/HttpClient/Message/QueryStringBuilderTest.php

@@ -49,6 +49,7 @@ public function queryStringProvider()
                 'target_project_id' => null,
                 'description'       => null
             ],
+            'source_branch=test_source&target_branch=test_master&title=test'
         ];
 
         //Boolean encoding