fix the build with -no-qml-debug

The "cleanup" variable doesn't exist in this case.

Change-Id: Ia7ed654d5c9ae57bc3f7cff39acbd72214ff4188
Reviewed-by: Ulf Hermann <ulf.hermann@theqtcompany.com>

src/qml/debugger/qqmldebugserver.cpp

@@ -460,7 +460,6 @@ QQmlDebugServer::QQmlDebugServer()
         }
     }
 #else
-    Q_UNUSED(&cleanup)
     if (!appD->qmljsDebugArgumentsString().isEmpty()) {
         qWarning() << QString(QLatin1String(
                      "QML Debugger: Ignoring \"-qmljsdebugger=%1\". "