fix: time unit in PeriodicCleanerExpectationManager and integration test #6042

Job	Run time
sample_operators_tests (sample-operators/webpage)	3m 23s
sample_operators_tests (sample-operators/tomcat-operator)	2m 49s
sample_operators_tests (sample-operators/leader-election)	3m 15s
sample_operators_tests (sample-operators/mysql-schema)	2m 42s
	12m 9s

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