Clarify text shown in a11y service warning dialog

Replacing the text generated from the service's
capabilities (which could change) with a generic message
based on the maximum capabilities (full control) a service
can obtain.

Bug: 110715236
Test: atest SettingsRoboTests
Change-Id: Iecb548c77c9031626d4da24741ec1f753d0cc94f
3 files changed