Bump pbr from 5.11.1 to 6.0.0 (#11188)

Bumps [pbr](https://docs.openstack.org/pbr/latest/

) from 5.11.1 to 6.0.0.

---
updated-dependencies:
- dependency-name: pbr
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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