test/rbd-mirror: eliminate a race in ResyncRequestedRemoteNotPrimary

test/rbd-mirror: eliminate a race in ResyncRequestedRemoteNotPrimary

Adjust the wait_for_notification call in TestMockImageReplayerSnapshotReplayer.ResyncRequestedRemoteNotPrimary
to expect 2 notifications instead of 1. This allows the test to correctly wait for both expected events
i.e for finish_sync() and handle_replay_complete(locker, -EREMOTEIO, "remote image demoted"), ensuring the
replayer transitions to STATE_COMPLETE and is_replaying() returns false as intended.

Fixes: https://tracker.ceph.com/issues/72325
Signed-off-by: VinayBhaskar-V <vvarada@redhat.com>