chore(deps): bump authlib from 1.6.8 to 1.6.12 in /agents/canvas

Bumps [authlib](https://github.com/authlib/authlib) from 1.6.8 to 1.6.12.
- [Release notes](https://github.com/authlib/authlib/releases)
- [Changelog](https://github.com/authlib/authlib/blob/1.6.12/docs/changelog.rst)
- [Commits](authlib/authlib@v1.6.8...1.6.12)

---
updated-dependencies:
- dependency-name: authlib
  dependency-version: 1.6.12
  dependency-type: direct:production
...

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Author: dependabot[bot]