Fix Introspector trial build (#8971)
Fix Introspector trial build (#8971)

Skip using `-testing` bucket as it breaks coverage download under
`trial_build`.
google/oss-fuzz,google/oss-fuzz,google/oss-fuzz,google/oss-fuzz,google/oss-fuzz,google/oss-fuzz,google/oss-fuzz,google/oss-fuzz,google/oss-fuzz,google/oss-fuzz,google/oss-fuzz