Bump nltk from 3.8.1 to 3.9.1 in /docker/py3-native (#31317)

Bumps [nltk](https://github.com/nltk/nltk) from 3.8.1 to 3.9.1.
- [Changelog](https://github.com/nltk/nltk/blob/develop/ChangeLog)
- [Commits](nltk/nltk@3.8.1...3.9.1)

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

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>