chore: set fastapi in env when running fastapi dojo examples

Author: ranst91

typescript-sdk/integrations/langgraph/examples/python/agents/dojo.py

@@ -5,7 +5,7 @@
 from dotenv import load_dotenv
 load_dotenv()
 
-os.environ["IS_FASTAPI"] = "true"
+os.environ["LANGGRAPH_FAST_API"] = "true"
 
 from ag_ui_langgraph import LangGraphAgent, add_langgraph_fastapi_endpoint
 from .human_in_the_loop.agent import graph as human_in_the_loop_graph