Toolbar: remove some unnecessary CSS lines.

They were commented out in `admin-bar.css` since 3 years, see [26770].

Props kafleg, ketuchetan.

Fixes #39137.

Built from https://develop.svn.wordpress.org/trunk@39533


git-svn-id: https://core.svn.wordpress.org/trunk@39473 1a063a9b-81f0-0310-95a4-ce76da25c4cd