Theme Version: You are likely using sphinx-rtd-theme v3.0+, which removed display_version in favor of more modern version-handling tools.

The Warning: Sphinx flags any key it doesn't recognize inside html_theme_options. By deleting it, you stop the theme from trying to process an unknown variable.

Impact: Since the option was already "unsupported," removing the line won't change how your documentation looks; it just stops the build logs from being cluttered.