Remove unused SmsManager API.

This API can be called to send messages without persisting it
in SMB db, and does not require any permission. It is not a public
API and is not used by any app per go/nonsdk-dash-per-api

Test: TH
Bug: 195311502
Change-Id: I06c63024de7e44b4aa7cb43d72b2f298c8355118