Clean up Communal Manager READ_COMMUNAL_STATE APIs.

These are not yet used, and are obsolete now because We will no longer
be shipping SLS in T.

Ignore-AOSP-First: tied to launch of new upcoming hardware.

Test: atest FrameworksMockingServicesTests:CommunalManagerServiceTest

Bug: 206054365
Change-Id: I51ffbfe5ddc89008d660fab7cfd5808cb827d300