QmlDesigner: Use ";" as delimiter for QMLDESIGNER_RC_PATHS

This is what is used in the qml2puppet.

Change-Id: I5c9ce65863539395d0f2c56e7be89998fd26f341
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>

src/plugins/qmldesigner/designercore/instances/nodeinstanceserverproxy.cpp

@@ -344,7 +344,7 @@ QString NodeInstanceServerProxy::qrcMappingString() const
 
             foreach (const StringPair &pair, rewriterView->qrcMapping()) {
                 if (!mappingString.isEmpty())
-                    mappingString.append(QLatin1String(","));
+                    mappingString.append(QLatin1String(";"));
                 mappingString.append(pair.first);
                 mappingString.append(QLatin1String("="));
                 mappingString.append(pair.second);