TextEditor: Modernize

override, auto, nullptr, member initializers.

Change-Id: I04c6ebb683849568973bd7782fb5a3279267141e
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/texteditor/snippets/snippetscollection.h

@@ -48,7 +48,7 @@ class SnippetsCollection : public QObject
 {
     Q_OBJECT
 public:
-    virtual ~SnippetsCollection();
+    ~SnippetsCollection() override;
 
     static SnippetsCollection *instance();