Fix: Removed the stray 's' and added a unit test to lock the formatting.

[Nandann018-ux]

This PR fixes a typo in FileSyntaxError.__str__ that caused user-facing error messages to show an incorrect line number prefix, and adds a unit test to lock the correct formatting. It also includes a newsfragment for the bugfix.

Was generative AI tooling used to co-author this PR?

Yes

Read the Pull Request Guidelines for more information. Note: commit author/co-author name and email in commits become permanently public when merged.
For fundamental code changes, an Airflow Improvement Proposal (AIP) is needed.
When adding dependency, check compliance with the ASF 3rd Party License Policy.

For significant user-facing changes create newsfragment: {pr_number}.significant.rst, in airflow-core/newsfragments. You can add this file in a follow-up commit after the PR is created so you know the PR number.

[potiuk]

You have some unrelated changes - can you please rebase and remove of those?

[Nandann018-ux]

Thanks for the heads‑up! I’ve rewritten the PR branch to include only the FileSyntaxError fix + test + newsfragment, rebased on apache/main. All unrelated commits are removed now. Could you please take another look?

[Nandann018-ux]

@jscheffl
Thanks for catching that , I’ve removed the newsfragment and updated the PR.

[boring-cyborg]

Awesome work, congrats on your first merged pull request! You are invited to check our Issue Tracker for additional contributions.

[github-actions]

Backport successfully created: v3-1-test

Note: As of Merging PRs targeted for Airflow 3.X
the committer who merges the PR is responsible for backporting the PRs that are bug fixes (generally speaking) to the maintenance branches.

In matter of doubt please ask in #release-management Slack channel.

Status	Branch	Result
✅	v3-1-test