Adwaita.css: Sidebar Unmount Icon Color Style

The unmount icon for a device was displayed in inverted color when the device was selected in the sidebar.
Applied styling to use the same theme color as other selected icons.
Fixes #645
3 jobs for master in 8 minutes and 1 second (queued for 2 seconds)
Status Job ID Name Coverage
  Test
passed #187493
flatpak devel

00:07:18

8.7%
 
  Deploy
passed #187494
pages

00:00:42

passed pages:deploy

00:00:00