ProjectExplorer: Use override consistently

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

Change-Id: I216701aec0b4134321e220f9e599e053a8e22945
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

src/plugins/projectexplorer/projectwindow.h

@@ -56,7 +56,7 @@ class ProjectWindow : public Utils::FancyMainWindow
 
 public:
     ProjectWindow();
-    ~ProjectWindow();
+    ~ProjectWindow() override;
 
 private:
     ProjectWindowPrivate *d;