chore: make library generation IT non-required #9687

Job	Run time
build(21) except self-service clients	13m 14s
build (11)	14m 48s
build(8) for gapic-generator-java	11m 16s
build (17)	14m 44s
compatibility	1m 22s
build(8) except for gapic-generator-java	4m 20s
lint	22s
dependency_analyzer_unit_test	17s
gapic-generator-java-bom	1m 46s
showcase (11)	4m 19s
showcase (17)	4m 20s
showcase-clirr	3m 2s
showcase (21)	4m 20s
showcase-native	8m 35s
unmanaged_dependency_check	4m 4s
	1h 30m 49s

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