Fix deletion visibility in region migration IT #29946

Job	Run time
unit-test (17, ubuntu-latest, datanode)	22m 9s
unit-test (17, windows-latest, datanode)	33m 57s
unit-test (17, windows-latest, others)	23m 36s
unit-test (17, ubuntu-latest, others)	19m 27s
	1h 39m 9s

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