Accessibility: Make links in the Customizer underlined by default.

Links within lines or blocks of text should always be underlined since they can't
rely on color alone to be distinguished from the surrounding text. Exceptions
can be handled on a case-by-case basis.

Props Presskopp for the initial patch.
Fixes #37527.

Built from https://develop.svn.wordpress.org/trunk@38503


git-svn-id: http://core.svn.wordpress.org/trunk@38444 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/css/customize-controls.css

@@ -3,7 +3,8 @@ body {
 	-webkit-text-size-adjust: 100%;
 }
 
-#customize-controls a {
+.customize-controls-close,
+.widget-control-actions a {
 	text-decoration: none;
 }