Classic: update window-list styling

- flatter, rounder to match default styling
- more contrast for the workspace applet
2 jobs for wip/jimmac/duller-classic-mode in 1 minute and 12 seconds (queued for 2 seconds)
latest
Status Job ID Name Coverage
  Source Check
passed #356291
eslint

00:00:34

 
  Build
passed #356292
build-shell-extensions

00:00:37