Telecom API doc cleanup.

InCallService - remove references to roles cut in Q release.
TelecomManager - make it more clear how to use the silenceRinger method
and under which conditions it should be used.

Test: Compile; docs only.
Fixes: 130285730
Change-Id: I55f9c2df119140666f8167e8521a4372d1108e7a
Merged-In: I3e55166e4d0d9e68449ac7c157959e8471c16354