Fix warning in tst_qopengl.cpp

This fixes warning: unused parameter ‘glFormat’

Change-Id: I4865300fb99ea5392b96f8e9f4f594f15f18625c
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>

tests/auto/gui/qopengl/tst_qopengl.cpp

@@ -642,6 +642,8 @@ static bool supportsInternalFboFormat(QOpenGLContext *ctx, int glFormat)
                 return false;
         }
     }
+#else
+    Q_UNUSED(glFormat);
 #endif
     return true;
 }