TextEditor: Use override consistently

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

Change-Id: Ie98c08279d7bf01f2705f631500dcabac5ba85d1
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/texteditor/texteditorsettings.h

@@ -63,7 +63,7 @@ class TEXTEDITOR_EXPORT TextEditorSettings : public QObject
 
 public:
     TextEditorSettings();
-    ~TextEditorSettings();
+    ~TextEditorSettings() override;
 
     static TextEditorSettings *instance();