chore(main): release 2.21.5

[release-please[bot]]

:robot: I have created a release beep boop

2.21.5 (2024-06-20)

Bug Fixes

• Allow Protobuf 5.x (a369f04)

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[release-please[bot]]

:robot: Created releases:

• v2.21.5 :sunflower:

[release-trigger[bot]]

Triggered job: cloud-devrel/client-libraries/python/googleapis/python-pubsub/release/release (2024-06-20T16:59:50.609Z)

To trigger again, remove the autorelease: triggered label (in a few minutes).

[release-tool-publish-reporter[bot]]

The release build has started, the log can be viewed here. :sunflower:

[release-tool-publish-reporter[bot]]

:egg: You hatched a release! The release build finished successfully! :purple_heart: