Upgrade/Install: Use new default admin color scheme for links on the setup screen.

This changeset updates the link colors on the setup screen and the default `wp_die()` fallback styles to use the new default admin color scheme.

Props audrasjb, darshitrajyaguru97, dhrumilk, hbhalodia, huzaifaalmesbah, ismail0071, mikinc860, pooja-n, shailu25, sumitsingh, vishitshah, wildworks
Fixes #64962. See #64308.

git-svn-id: https://develop.svn.wordpress.org/trunk@62230 602fd350-edb4-49c9-b593-d223f7449a82