Follows-up e58be7c411, 1ad0c9c819.
* The mw.uls.eventlogger property does not appear to be
used anywhere indexed by Codesearch. It was also undocumented.
Removed without deprecation. Kept exposed for debugging purpopses
via module.exports, which could be retreived in tests via require(),
or via mw.loader.require() from the browser console.
* Remove redundant $.Deferred wrapper.
Change-Id: Id081038e5d4902c7e38967353c6f551c12517311
1c99196ef8