Remove declaration of method nowhere defined

Change-Id: Ia95aac626803a85fea0bc0bc99972eb34215d351
Reviewed-by: Jędrzej Nowacki <jedrzej.nowacki@theqtcompany.com>

src/corelib/plugin/qfactoryloader.cpp

@@ -79,8 +79,6 @@ public:
     QString suffix;
     Qt::CaseSensitivity cs;
     QStringList loadedPaths;
-
-    void unloadPath(const QString &path);
 };
 
 QFactoryLoaderPrivate::~QFactoryLoaderPrivate()