refactor(google-photos): replace generated classes with variables

[WalkQuackBack]

🔧 What does this fix? 🔧

Refactors Google Photos to remove most generated colour classes in exchange for variables. However, this does change the look of the site matching M3 guidelines. Before and after images are attached below for reference.

Images

I would also like to add myself as a maintainer of the userstyle.

🗒 Checklist 🗒

• [x] I have read and followed Catppuccin's contributing guidelines.