Improve google-calendar's darkmode styling

[eitchtee]

Pre-flight Checklist

Please ensure you've completed all of the following.

• [x] I have read the Contributing Guidelines for this project.
• [x] I agree to follow the Code of Conduct that this project adheres to.
• [x] I updated the version package Updating

Description of Change

This updates google-calendar's darkmode's css to use the styling from https://github.com/EvHaus/google-redesigned, a more maintained and good-looking version.

Screenshots

See https://github.com/ferdium/ferdium-app/issues/1846 for how it looks right now

You can demo this change by inserting https://raw.githack.com/eitchtee/google-redesigned-ferdium/master/css/calendar.user.css on your own google-calendar webview.js as I've been keeping a version of this styling for my own use on Ferdium for quite some time now.

fixes https://github.com/ferdium/ferdium-app/issues/1846