RESTRICT AUTOMERGE Unregister receiver in RollbackManagerServiceImpl

Receiver not unregistered when user_removed, this cause the
system_server reach the MAX_RECEIVERS_ALLOWED_PER_APP limit
and system_server crashed. This issue happens only when user
is in demo mode and do Suspend/Resume cycles where new user
creates on suspend.

Fix this by unregister the receiver when user_removed.

Test: User is in demo mode and do STR cycles (Suspend and
      Resume) loop test.

Bug: 330203379
Change-Id: Ib01b209ccbb69cb54aac03b0a13f86d794a9bc33