pubsub: fix package name in go_mod_tidy_hack.go
pubsub: fix package name in go_mod_tidy_hack.go

This will be tagged pubsub/v1.0.1.

Change-Id: Ifd6d6b2fd181872197265fa81b0b904e47edbc2e
Reviewed-on: https://code-review.googlesource.com/c/gocloud/+/44851
Reviewed-by: Alex Hong <3311379d571f0e1dc66d44c9732cbfa024b0fda6@google.com>

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