Core: Use override consistently

clang-tidy fixes from modernize-use-override check.

Change-Id: If33399d60e96cae766bbedbe30044ada411e862f
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/coreplugin/vcsmanager.h

@@ -108,7 +108,7 @@ signals:
 
 private:
     explicit VcsManager(QObject *parent = 0);
-    ~VcsManager();
+    ~VcsManager() override;
 
     static void addVersionControl(IVersionControl *vc);