ci: fix library generation presubmit #1171

Job	Run time
filter	1m 2s
build(8) for gapic-generator-java	6m 49s
build (17)	9m 19s
build(21) except self-service clients	12m 2s
build (11)	9m 35s
build(8) for showcase	10m 42s
build(8) except for gapic-generator-java	3m 47s
gapic-generator-java-bom	4m 40s
showcase-clirr	5m 11s
dependency_analyzer_unit_test	1m 17s
unmanaged_dependency_check	15m 16s
build(25) except self-service clients	9m 50s
showcase (25)	12m 44s
showcase (11)	14m 8s
showcase (21)	14m 4s
showcase (17)	13m 33s
	2h 23m 59s

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