deps: update dependency com.google.api-client:google-api-client-bom to v2.7.1 #9523

Job	Run time
build(21) except self-service clients	13m 17s
build (11)	14m 46s
build(8) except for gapic-generator-java	4m 20s
build(8) for gapic-generator-java	11m 15s
build (17)	14m 51s
dependency_analyzer_unit_test	18s
gapic-generator-java-bom	1m 52s
lint	28s
compatibility	1m 33s
showcase (11)	4m 13s
showcase-clirr	3m 1s
showcase-native	8m 41s
showcase (17)	4m 15s
showcase (21)	4m 14s
unmanaged_dependency_check	7m 9s
	1h 34m 13s

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