docs: fix broken settings table

[browniebroke]

What does this PR do?

The settings table is not rendering on this page: https://django-axes.readthedocs.io/en/latest/4_configuration.html

Looks like I broke the rendering of the settings table in my previous PR #1222 🤦🏻
It's because the closing | of the AXES_COOLOFF_TIME row is not aligned with the other rows in the table

Before submitting

• [x] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
• [ ] Did you make sure to update the documentation with your changes?
• [ ] Did you write any new necessary tests?

[aleksihakli]

Thank you, looks good 👍