Docs fail to build because of the new PyData Theme navigation_with_keys warning

[jtpio]

Problem

In #1227 the docs fail to build because of the following warning:

WARNING: The default value for `navigation_with_keys` will change to `False` in the next release. If you wish to preserve the old behavior for your site, set `navigation_with_keys=True` in the `html_theme_options` dict in your `conf.py` file.Be aware that `navigation_with_keys = True` has negative accessibility implications:https://github.com/pydata/pydata-sphinx-theme/issues/1492

Suggested Improvement

We can set the default to False as suggested and because the theme defaults to False if not specified:

"navigation_with_keys": False

Related PR: pydata/pydata-sphinx-theme#1503