Fix typo in docstring.

[stefmolin]

Hey, I just made a Pull Request!

Description

I noticed there was an extraneous k at the end of the find_project_root() docstring.

Motivation and Context

Fix a typo.

Have you tested this? If so, how?

N/A

Checklist for PR author(s)

• [x] Changes are covered by unit tests (no major decrease in code coverage %).
• [x] All tests pass.
• [x] Docstring coverage is 100% via tox -e docs or interrogate -c pyproject.toml (I mean, we should set a good example :smile:).
• [x] Updates to documentation:
  • [x] Document any relevant additions/changes in README.rst.
  • [x] Manually update both the README.rst and docs/index.rst for any new/changed CLI flags.
  • [x] Any changed/added classes/methods/functions have appropriate versionadded, versionchanged, or deprecated directives. Find the appropriate next version in the project's __init__.py file.

Release note