Fix: Add missing huggingface-hub dependency

The previous commit to update the embedding model resulted in an
ImportError because `sentence-transformers` could not import
`huggingface-hub`.

This commit explicitly adds `huggingface-hub==0.0.8` to
`requirements.txt`. This version is a dependency of
`transformers==4.6.0`, which is recommended by
`sentence-transformers==2.2.2`.

This should resolve the import error and allow the application
to start correctly with the new embedding model.

requirements.txt

@@ -5,3 +5,4 @@ pandas
 openai 
 sentence-transformers==2.2.2
 torch==2.2.0
+huggingface-hub==0.0.8