js: Remove an outdated reference to the "invisible Custom option"

emcc.c

@@ -750,10 +750,7 @@ static void cfg_end(bool use_results)
          * select Custom from the list, but change your mind and hit
          * Esc. The Custom option will now still be selected in the
          * list, whereas obviously it should show the preset you still
-         * _actually_ have selected. Worse still, it'll be the visible
-         * rather than invisible Custom option - see the comment in
-         * js_add_preset in emcclib.js - so you won't even be able to
-         * select Custom without a faffy workaround.)
+         * _actually_ have selected.)
          */
         select_appropriate_preset();