qmlpreview: fix init locale issue

The init language was never found, because the
findValidI18nDirectoryAsUrl() uses the m_lastLoadedUrl
to find the translation file path.

Change-Id: I6e9b62f3d846795d68ddef5e3a4caf3e3d953c7c
Reviewed-by: Marco Bubke <marco.bubke@qt.io>

src/plugins/qmlpreview/qmlpreviewruncontrol.h

@@ -39,7 +39,7 @@ class QmlPreviewRunner : public ProjectExplorer::RunWorker
 public:
     QmlPreviewRunner(ProjectExplorer::RunControl *runControl, QmlPreviewFileLoader fileLoader,
                      QmlPreviewFileClassifier fileClassifier, QmlPreviewFpsHandler fpsHandler,
-                     float initialZoom, const QString &initialLocale);
+                     float initialZoom);
 
     void setServerUrl(const QUrl &serverUrl);
     QUrl serverUrl() const;