VcsBase: Add missing override modifier.

Change-Id: I15ef5783e16c0e92262e05f8dace169f879228f8
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

src/plugins/vcsbase/vcsbaseeditor.h

@@ -241,7 +241,7 @@ private slots:
     void slotPopulateDiffBrowser();
     void slotPopulateLogBrowser();
     void slotJumpToEntry(int);
-    void slotCursorPositionChanged();
+    void slotCursorPositionChanged() override;
     void slotAnnotateRevision();
     void slotApplyDiffChunk();
     void slotPaste();