pinning RAG chatbot requirements

demo_apps/OctoAI_API_examples/RAG_Chatbot_example/requirements.txt

@@ -1,7 +1,7 @@
-gradio
-pypdf
-langchain
-sentence-transformers
-faiss-cpu
-text-generation
-octoai-sdk
+gradio==4.16.0
+pypdf==4.0.0
+langchain==0.1.7
+sentence-transformers==2.2.2
+faiss-cpu==1.7.4
+text-generation==0.6.1
+octoai-sdk==0.8.3