Update to jQuery 1.11

This does the small amount needed to migrate Review Board to jQuery 1.11.

Testing done:
- Ran js-tests.
- Grepped through the javascript code and audited against the list of
  backwards-incompatible changes in jQuery 1.9 (1.10 and 1.11 are pretty
  trivial in terms of incompatible changes).

Reviewed at https://reviews.reviewboard.org/r/6700/