cleanup: Require "dangling" commas

Since ES5, trailing commas in arrays and object literals are valid.
We generally haven't used them so far, but they are actually a good
idea, as they make additions and removals in diffs much cleaner.

https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/805

js/ui/components/autorunManager.js

@@ -20,7 +20,7 @@ var AutorunSetting = {
     RUN: 0,
     IGNORE: 1,
     FILES: 2,
-    ASK: 3
+    ASK: 3,
 };
 
 // misc utils