deps: update dependency org.easymock:easymock to v5.4.0 #7573

Job	Run time
build(21) except self-service clients	13m 31s
build (11)	15m 21s
build (17)	14m 51s
build(8) except for gapic-generator-java	4m 23s
compatibility	1m 37s
build(8) for gapic-generator-java	11m 34s
lint	36s
dependency_analyzer_unit_test	15s
gapic-generator-java-bom	1m 53s
showcase (11)	4m 18s
showcase-clirr	3m 11s
showcase (17)	4m 0s
showcase (21)	4m 11s
showcase-native	8m 11s
unmanaged_dependency_check	7m 16s
	1h 35m 8s

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