Update gpt4all_chat.md (#597)

Signed-off-by: Andriy Mulyar <andriy.mulyar@gmail.com>

gpt4all-bindings/python/docs/gpt4all_chat.md

@@ -24,7 +24,7 @@ import openai
 openai.api_base = "http://localhost:4891/v1" 
 #openai.api_base = "https://api.openai.com/v1"
 
-# Read the OpenAI API key from an environment variable
+# Read the OpenAI API key from an environment variable (not needed if using local LLM)
 openai_api_key = os.environ.get("OPENAI_API_KEY")
 if not openai_api_key:
     raise ValueError("Please set the 'OPENAI_API_KEY' environment variable.")