Typo in tracing.md

[dingkwang]

Describe the bug

A typo in the tracing.md's code example

Debug information

• Agents SDK version:v0.0.3

Repro steps

    with trace("Joke workflow"): # (1)!
        first_result = await Runner.run(agent, "Tell me a joke")
        second_result = await Runner.run(agent, f"Rate this joke: {first_output.final_output}")

Expected behavior

A clear and concise description of what you expected to happen.

    with trace("Joke workflow"): # (1)!
        first_result = await Runner.run(agent, "Tell me a joke")
        second_result = await Runner.run(agent, f"Rate this joke: {first_result.final_output}")

[dingkwang]

Resolved per #108