Update jquery.i18n from upstream, use its default message store

In Iddef0805ab a custom message store was introduced for ULS, but
there were updates in jquery.i18n that allows us to use default
message store again.

(see https://github.com/wikimedia/jquery.i18n/pull/40)

Change-Id: I86cb7a44efa83e5811824cd1104c6be11b1e2925