chore(deps): bump nltk

Bumps [nltk](https://github.com/nltk/nltk) from 3.9.1 to 3.9.4.
- [Changelog](https://github.com/nltk/nltk/blob/develop/ChangeLog)
- [Commits](nltk/nltk@3.9.1...3.9.4)

---
updated-dependencies:
- dependency-name: nltk
  dependency-version: 3.9.4
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]