Bump nltk from 3.8.1 to 3.9 in /adi_function_app (#13)

Bumps [nltk](https://github.com/nltk/nltk) from 3.8.1 to 3.9.
- [Changelog](https://github.com/nltk/nltk/blob/develop/ChangeLog)
- [Commits](nltk/nltk@3.8.1...3.9)

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

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adi_function_app/requirements.txt

@@ -9,7 +9,7 @@ pandas
 azure-identity
 openpyxl
 regex
-nltk==3.8.1
+nltk==3.9
 bs4
 azure-search
 azure-search-documents