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/textdocumentlayout.h

@@ -68,7 +68,7 @@ public:
         , m_foldingEndIncluded(false)
         , m_codeFormatterData(nullptr)
     {}
-    ~TextBlockUserData();
+    ~TextBlockUserData() override;
 
     inline TextMarks marks() const { return m_marks; }
     void addMark(TextMark *mark);