TextEditor: cleanup annotation rect cache after mark is removed

Change-Id: I8a0ab2df9d310da6025325ab3114eeadabfd4fb1
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/texteditor/textdocument.h

@@ -144,6 +144,7 @@ signals:
     void contentsChangedWithPosition(int position, int charsRemoved, int charsAdded);
     void tabSettingsChanged();
     void fontSettingsChanged();
+    void markRemoved(TextMark *mark);
 
 protected:
     virtual void applyFontSettings();