[pyupgrade] Avoid syntax error when the iterable is an non-parenthesized tuple (UP028)

[InSyncWithFoo]

Summary

Resolves #15540.

Test Plan

cargo nextest run and cargo insta test.

[github-actions]

ruff-ecosystem results

Linter (stable)

✅ ecosystem check detected no linter changes.

Linter (preview)

✅ ecosystem check detected no linter changes.

[charliermarsh]

Thanks, this makes sense to me.

[charliermarsh]

I think an unparenthesized generator might have a similar problem, but isn't syntactically valid in the for, like:

for _ in x for y in z:
    pass