Upgrade gpt-4-32k to GPT-4-Turbo (128K context length) for cost red…

…uction (#313)

### Description
- it is 6 times cheaper to use gpt-4 turbo the newer model with 128k
context length than gpt-4-32k
- it is also more performant
- Changed model temperature as well since high temperature does not make
sense. We do not need extract entropy or "creativity" in the response
for RAG apps

closes #314

api/ask_astro/settings.py

@@ -15,10 +15,10 @@
 
 # Environment variables for ConversationalRetrievalChain Load QA Chain
 CONVERSATIONAL_RETRIEVAL_LOAD_QA_CHAIN_TEMPERATURE = float(
-    os.environ.get("CONVERSATIONAL_RETRIEVAL_LOAD_QA_CHAIN_TEMPERATURE", "0.5")
+    os.environ.get("CONVERSATIONAL_RETRIEVAL_LOAD_QA_CHAIN_TEMPERATURE", "0.3")
 )
 CONVERSATIONAL_RETRIEVAL_LOAD_QA_CHAIN_DEPLOYMENT_NAME = os.environ.get(
-    "CONVERSATIONAL_RETRIEVAL_LOAD_QA_CHAIN_DEPLOYMENT_NAME", "gpt-4-32k"
+    "CONVERSATIONAL_RETRIEVAL_LOAD_QA_CHAIN_DEPLOYMENT_NAME", "gpt-4-128k"
 )
 
 SHOW_SERVICE_MAINTENANCE_BANNER = os.environ.get("SHOW_SERVICE_MAINTENANCE_BANNER", "False").upper() == "TRUE"