audio policy: fix capture policy for accessibility

Do not consider Accessibility services when determining
lastest active capture client. As an Accessibility service
capturing does not silence other captures, it should not
prevent another client from being selected as the latest active.

Bug: 135806801
Test: Start capture with Recorder app, activate Voice Access
Change-Id: I864be785752f27201d45ce24f95013de6391dbd6
Merged-In: I864be785752f27201d45ce24f95013de6391dbd6