Update header test to 'Work profile input & assistance'

Per suggestion from UX, this CL updates the category header of
work-profile specific enties in Languages & input from
  Work profile
to
  Work profile input & assistance.

Other than that, there is no user-visible behavior change.

Bug: 123314089
Test: Manually verified as follows.
  1. Build and flash an AOSP build
  2. Install Test DPC
  3. Open Settings -> System -> Languages & input
  4. Make sure that the new category header for work-profile specific
     entries is now shown as "Work profile input & assistance"
Change-Id: I4a4fb7c8a31d8d849780e71796b92ec0a2f026e3