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/idocumentfactory.h

@@ -42,7 +42,7 @@ class CORE_EXPORT IDocumentFactory : public QObject
 
 public:
     IDocumentFactory(QObject *parent = nullptr);
-    ~IDocumentFactory();
+    ~IDocumentFactory() override;
 
     static const QList<IDocumentFactory *> allDocumentFactories();