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/portalHelper/main.js

@@ -11,13 +11,13 @@ const { loadInterfaceXML } = imports.misc.fileUtils;
 const PortalHelperResult = {
     CANCELLED: 0,
     COMPLETED: 1,
-    RECHECK: 2
+    RECHECK: 2,
 };
 
 const PortalHelperSecurityLevel = {
     NOT_YET_DETERMINED: 0,
     SECURE: 1,
-    INSECURE: 2
+    INSECURE: 2,
 };
 
 const CONNECTIVITY_CHECK_HOST = 'nmcheck.gnome.org';