Revert "Removed deprecated function"

This reverts commit 93e243c4

widgets/codeeditor.cc

@@ -71,7 +71,7 @@ int CodeEditorWidget::lineNumberAreaWidth() {
     ++digits;
   }
 
-  int space = 3 + fontMetrics().horizontalAdvance(QLatin1Char('9')) * digits;
+  int space = 3 + fontMetrics().width(QLatin1Char('9')) * digits;
 
   return space;
 }