Add missing key in sample

Author: pamelafox

.env.sample

@@ -18,6 +18,8 @@ AZURE_OPENAI_CHAT_MODEL=gpt-35-turbo
 AZURE_OPENAI_EMBED_DEPLOYMENT=text-embedding-ada-002
 AZURE_OPENAI_EMBED_MODEL=text-embedding-ada-002
 AZURE_OPENAI_EMBED_MODEL_DIMENSIONS=1536
+# Only needed when using key-based Azure authentication:
+AZURE_OPENAI_KEY=
 # Needed for OpenAI.com:
 OPENAICOM_KEY=YOUR-OPENAI-API-KEY
 OPENAICOM_CHAT_MODEL=gpt-3.5-turbo