Update crewai/agent.py

add environment variable for the api key

crewai/agent.py

@@ -72,6 +72,7 @@ class Agent(BaseModel):
         default_factory=lambda: ChatOpenAI(
             temperature=0.7,
             model_name="gpt-4-1106-preview",
+                openai_api_key=os.getenv("OPENAI_API_KEY")
         ),
         description="Language model that will run the agent.",
     )