QmakeProjectManager: Use override consistently

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

Change-Id: If75d8ae6b75edf271602e9352ea4cfac849c40ee
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

src/plugins/qmakeprojectmanager/customwidgetwizard/classlist.h

@@ -59,7 +59,7 @@ private:
     void slotCurrentRowChanged(const QModelIndex &,const QModelIndex &);
 
 protected:
-    void keyPressEvent(QKeyEvent *event);
+    void keyPressEvent(QKeyEvent *event) override;
 
 private:
     ClassModel *m_model;