Add missing @since 7.7

Change-Id: Id9f1dbc991c1dcb2c2d3817d9d958485db6269bc

client/src/main/java/com/vaadin/client/ui/VFilterSelect.java

@@ -903,7 +903,7 @@ public class VFilterSelect extends Composite implements Field, KeyDownHandler,
         }
 
         /**
-         * @since
+         * @since 7.7
          * @param suggestionPopupWidth
          * @return
          */