fix jquery-ui autocomplete to repsect aria-label

incorporates changes made in more recent versions of jquery-ui that respect the
aria-label on the menu items if it is given, rather than hardcoding to always
read the value entered in the text field.

see github.com/jquery/jquery-ui/commit/0b28d597fe1857590c9719c8b41f00e77967f7d7

fixes CNVS-12153

test plan:
- spot check a few places that use the jqueryui autocomplete widget (e.g. find
  a course on the account page and content migrations page)
- you shouldn't see any change (this just enables future expansion to build
  more rich autocomplete ux that is accessible)

Change-Id: I40e6bb097000d5df6ffc442684fbf0b792392bc6
Reviewed-on: https://gerrit.instructure.com/32689
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Stanley Stuart <stanley@instructure.com>
QA-Review: Amber Taniuchi <amber@instructure.com>
Product-Review: Simon Williams <simon@instructure.com>