Fix macOS installation

[scottnuma]

• macOS installation broke due to nokogiri. nokogiri is no fun to install because it is a chonker of a package and has an involved installation process
• Move nokogiri and htmlproofer into the test group because they are used for testing
• Do not install these packages by default, also do not install in Docker
• Update the packages while we're at it

[render[bot]]

Your Render PR Server URL is https://website-staging-pr-631.onrender.com.

Follow its progress at https://dashboard.render.com/static/srv-c2uomou31hs7pm2g36f0.

[scottnuma]

thank you for the commit