revert: use fastembed>=0.7.0 with rerank module, remove huggingface_hub version constraint

requirements.txt

@@ -12,6 +12,7 @@ langchain-core>=0.3.0
 langchain-google-genai>=2.0.0
 langgraph>=0.2.0
 fastembed<0.7.0
+sentence-transformers>=2.2.0
 gradio==4.44.1
 huggingface_hub<0.20.0
 pydantic>=2.0.0