test: fix test_reject_proposal_during_region_merge (#10627)
test: fix test_reject_proposal_during_region_merge (#10627)

Signed-off-by: gengliqi <gengliqiii@gmail.com>

Co-authored-by: Ti Chi Robot <040e6455cde1c91e876ec337e785ce913eacba35@tidb.io>
BusyJay/tikv,BusyJay/tikv,BusyJay/tikv,BusyJay/tikv