Avoid asyncio-dangling-task violations on shadowed bindings

[charliermarsh]

Summary

Ensures that we avoid flagging cases like:

async def f(x: int):
    if x > 0:
        task = asyncio.create_task(make_request())
    else:
        task = asyncio.create_task(make_request())
    await task

Closes #9133.

[github-actions]

ruff-ecosystem results

Linter (stable)

✅ ecosystem check detected no linter changes.

Linter (preview)

✅ ecosystem check detected no linter changes.