tests: stablize test_notify_observer_after_apply (#9176)
tests: stablize test_notify_observer_after_apply (#9176)

Signed-off-by: youjiali1995 <c0aa3f5eb42bd3bf1adeeced4b718fc1900fde64@gmail.com>
BusyJay/tikv,BusyJay/tikv,BusyJay/tikv,pingcap/tikv,c4pt0r/tikv,BusyJay/tikv,pingcap/tikv