Bump cloud.google.com/go/pubsub from 1.19.0 to 1.20.0

Created by: dependabot[bot]

Bumps cloud.google.com/go/pubsub from 1.19.0 to 1.20.0.

Release notes

Sourced from cloud.google.com/go/pubsub's releases.

pubsub: v1.20.0

1.20.0 (2022-04-11)

Features

• pubsub/pstest: add topic retention support (#4790) (0a4ad6a)

Bug Fixes

• pubsub: ignore grpc errors in ack/modack (#5796) (4fb9aec)

Commits

• aa49b04 chore(main): release pubsub 1.20.0 (#5734)
• b2f1942 chore(internal/kokoro): Update vet.sh staticcheck (#5876)
• 74c120a feat(bigquery): support table cloning (#5672)
• a8fc2fa chore(main): release spanner 1.31.0 (#5870)
• 08f1e72 fix(spanner/spannertest): Improve DDL application delay cancellation. (#5874)
• c2510d7 docs(pubsublite): clarify publish error handling (#5864)
• dfda3e0 chore: bump storage dependencies to v1.22.0 (#5868)
• 4b191a6 chore(storage): refactor emulator tests, resolve some TODOs (#5869)
• bb5da6b chore(all): auto-regenerate gapics (#5865)
• 9360a6b test(bigquery): refactor integration tests (#5863)
• Additional commits viewable in compare view

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