internal: give tests more time
internal: give tests more time

Tests are bumping up to the 45m limit. Bump limit to 60m.

See: https://sponge.corp.google.com/target?id=a4aaa4db-d5af-442d-9308-f6cd064b4522&target=cloud-go-libraries/google-cloud-go/continuous/go112&searchFor=&show=ALL&sortBy=STATUS
Change-Id: I9a4118c071a9362378127cdbcf354e3d60a026a1
Reviewed-on: https://code-review.googlesource.com/c/gocloud/+/42291
Reviewed-by: Emmanuel Odeke <bd234ba4276433f0e5fc7a8fa2d18274fa711567@orijtech.com>

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