Partially undo failed revert of "Update jquery.ui Vector theme to 1.9.2"

Follows-up 36b8e0e10ff which claims to revert 7bb0c9a01e, but
really just made a gigantic mess of the place and managed to somehow
partially undo the jQuery UI upgrade to 1.9 (3cb2ccd87863abb8a) which
breaks in all kinds of interesting ways because the stylesheets
it added instead are from jQuery UI 1.8 and naturally incompatible.

This restores resources/lib/jquery.ui from the mediawiki-core
tree at 977b5ea0e090 (parent of 7bb0c9a01e).

Change-Id: Ie3bcd8560fe5012ed616fc341e036e8614b5208c