internal: reduce test time to 30m
internal: reduce test time to 30m

Average is 20m.

Change-Id: I02f1e5626a8cf1ef684da9152ab79d2cf7dd665a
Reviewed-on: https://code-review.googlesource.com/c/gocloud/+/42312
Reviewed-by: Emmanuel Odeke <bd234ba4276433f0e5fc7a8fa2d18274fa711567@orijtech.com>

googleapis/google-cloud-go,googleapis/google-cloud-go,googleapis/google-cloud-go,googleapis/google-cloud-go