binder: Delete addTrustedPeerCertificate.

For RpcServer and RpcSession, caller should retain
an ownership of the verifier when creating
RpcTransportCtxFactory, so APIs to addTrustedPeerCertificate
are deleted.

The logic to add certificates should be in the implementation
of RpcCertificateVerifier. See follow-up CLs.

Test: binderRpcTest
Bug: 198833574

Change-Id: If0ed87adfeee2ee48582604881ee335b5d689589