Gatekeeper no longer needs to access UserManager.

This is a revert of http://ag/741434

Bug: 38259874
Test: manually, using ConfirmCredential sample app.
Change-Id: I0cbb955110935de605cb90e26a6a1d851a93a4b8

public/gatekeeperd.te

@@ -29,9 +29,6 @@ allow gatekeeperd keystore:keystore_key { add_auth };
 allow gatekeeperd system_server:binder call;
 allow gatekeeperd permission_service:service_manager find;
 
-# For parent user ID lookup
-allow gatekeeperd user_service:service_manager find;
-
 # for SID file access
 allow gatekeeperd gatekeeper_data_file:dir rw_dir_perms;
 allow gatekeeperd gatekeeper_data_file:file create_file_perms;