chore: bump cloud.google.com/go/auth from 0.20.0 to 0.21.0

[dependabot]

Bumps cloud.google.com/go/auth from 0.20.0 to 0.21.0.

Release notes

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

agentplatform: v0.21.0

v0.21.0 (2026-05-27)

Features

• Add ListSkills and DeleteSkill methods in Vertex AI Skill Registry SDK (PiperOrigin-RevId: 912730700) (942bbc15)

Bug Fixes

• Fix name collision on SandboxEnvironment.state by renaming enum to SandboxState (PiperOrigin-RevId: 912527667) (14ea3de7)

• Set the agentplatform's dedicated user-agent in header. (PiperOrigin-RevId: 915113335) (66574dbb)

Documentation

• update README to reflect Gemini Enterprise Agent Platform (PiperOrigin-RevId: 912137130) (541569e8)

auth: v0.21.0

0.21.0 (2026-07-07)

Features

• auth: Implement updated design for regional access boundary (#13417) (fadb6c7)

Bug Fixes

• auth: Avoid double impersonation in idtoken and clarify docs (#14474) (995bfc3), closes #11105
• auth: Correct go min version (#20094) (6bb4358)

Changelog

Sourced from cloud.google.com/go/auth's changelog.

v0.21.0

• bigquery:

  • Add OpenCensus tracing.

• firestore:

  • BREAKING CHANGE: If a document does not exist, return a DocumentSnapshot whose Exists method returns false. DocumentRef.Get and Transaction.Get return the non-nil DocumentSnapshot in addition to a NotFound error. DocumentRef.GetAll and Transaction.GetAll return a non-nil DocumentSnapshot instead of nil.
  • Add DocumentIterator.Stop. Call Stop whenever you are done with a DocumentIterator.
  • Added Query.Snapshots and DocumentRef.Snapshots, which provide realtime notification of updates. See https://cloud.google.com/firestore/docs/query-data/listen.
  • Canceling an RPC now always returns a grpc.Status with codes.Canceled.

• spanner:

  • Add CommitTimestamp, which supports inserting the commit timestamp of a transaction into a column.

Commits

• 29f476f README: update news for next release
• 01301d1 firestore: remove test for codes.Canceled with RPC
• d53c437 internal/btree: add SetWithIndex
• 4d44512 dlp: update doc
• 7e2a57e profiler: reduce verbosity of e2e test output
• b475e33 internal: remove the use of deprecated OpenCensus APIs
• a708ebb internal/testutil: use OpenCensus trace.ApplyConfig instead of SetDefaultSampler
• 6cd8fd0 profiler: add integration test for go1.10
• a21236a Add James Hall to contributors
• 994ac59 firestore: handle canceled contexts uniformly
• Additional commits viewable in compare view

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[tiffanny29631]

/ok-to-test

[tiffanny29631]

/lgtm

[tiffanny29631]

/lgtm

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