autotest: Fix warning on missing override

Change-Id: I93acb387269e6ee02c968bea18f6ce347d18656a
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/autotest/testrunconfiguration.h

@@ -71,7 +71,7 @@ public:
     }
 
 private:
-    QWidget *createConfigurationWidget() { return 0; }
+    QWidget *createConfigurationWidget() override { return 0; }
     TestConfiguration *m_testConfig = 0;
 };