flaky test TestStoreRemoved

[hawkingrei]

Bug Report

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1. Minimal reproduce step (Required)

2. What did you expect to see? (Required)

3. What did you see instead (Required)

     subscription_test.go:171: 
        	Error Trace:	br/pkg/streamhelper/subscription_test.go:171
        	Error:      	Not equal: 
        	            	expected: 0x89b
        	            	actual  : 0x53c
        	Test:       	TestStoreRemoved
        	Messages:   	cp = 2203, s = 1340 

https://tiprow.hawkingrei.com/view/gs/pingcapprow/pr-logs/pull/pingcap_tidb/52663/fast_test_tiprow/1782248254419767296#1:build-log.txt%3A1603

4. What is your TiDB version? (Required)

[D3Hunter]

met again, seems it fails all the time

https://do.pingcap.net/jenkins/blue/organizations/jenkins/pingcap%2Ftidb%2Fghpr_unit_test/detail/ghpr_unit_test/8298/pipeline