Bump nltk from 3.6.1 to 3.6.5

Bumps [nltk](https://github.com/nltk/nltk) from 3.6.1 to 3.6.5.
- [Release notes](https://github.com/nltk/nltk/releases)
- [Changelog](https://github.com/nltk/nltk/blob/develop/ChangeLog)
- [Commits](nltk/nltk@3.6.1...3.6.5)

---
updated-dependencies:
- dependency-name: nltk
  dependency-type: direct:production
...

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

requirements.txt

@@ -2,7 +2,7 @@ Flask==1.1.2
 numpy==1.20.1
 scikit-learn==0.24.1
 pandas==1.2.4
-nltk==3.6.1
+nltk==3.6.5
 imbalanced-learn==0.8.0
 matplotlib==3.4.3
 matplotlib-inline==0.1.2