build(deps): bump tokenizers from 0.20.3 to 0.21.0

Bumps [tokenizers](https://github.com/huggingface/tokenizers) from 0.20.3 to 0.21.0.
- [Release notes](https://github.com/huggingface/tokenizers/releases)
- [Changelog](https://github.com/huggingface/tokenizers/blob/main/RELEASE.md)
- [Commits](huggingface/tokenizers@v0.20.3...v0.21.0)

---
updated-dependencies:
- dependency-name: tokenizers
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>