Revert "Add proximity state to the HotwordDetectedResult"

Revert submission 17936037-hotword_proximity

Reason for revert: https://buganizer.corp.google.com/issues/242223069
Reverted Changes:
If8c23a9c6:Refactor ProximityUpdateCallbackInternal to interf...
Ib0ad1da25:Verify that proximity key is added to the hotword ...
I71e9d3da9:Add proximity state to the HotwordDetectedResult

Change-Id: I6b79d9400671362dd63be1e2a0d05280003587d3