improve: rename junit5 module to junit #5999

Job	Run time
sample_operators_tests (sample-operators/tomcat-operator)	1m 40s
sample_operators_tests (sample-operators/mysql-schema)	1m 55s
sample_operators_tests (sample-operators/leader-election)	1m 42s
sample_operators_tests (sample-operators/webpage)	1m 48s
	7m 5s

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