DOC: Fix typo in firetask tutorial

[HaoZeke]

Summary

Major changes:

Just fixed a a documentation typo.

Todos

If this is work in progress, what else needs to be done?

N/A.

Checklist

• [X] Google format doc strings added. Check with ruff.
• [X] Type annotations included. Check with mypy.
• [X] Tests added for new features/fixes.
• [X] If applicable, new classes/functions/modules have duecredit @due.dcite decorators to reference relevant papers by DOI (example)

Tip: Install pre-commit hooks to auto-check types and linting before every commit:

pip install -U pre-commit
pre-commit install

None of the checklist apply.