Small documentation fix for graph.md Human in the loop example

[sarunas-llm]

With ai_q_and_a_graph.py given above ai_q_and_a_run.py code is wrong
answer: str | None = sys.argv[2] if len(sys.argv) > 2 else None should be answer: str | None = sys.argv[1] if len(sys.argv) > 1 else None
We only need 1 argument for answer, so explanation bellow (This example is complete, it can be run "as is" with Python 3.10+ — you'll need to add asyncio.run(main(answer)) to run main) is wrong.
Also asyncio.run(main(answer)) should be asyncio.run(main()) because main() in ai_q_and_a_run.py does not accept arguments.

PR #1280