Administration: Use a lighter font-weight value for settings labels.

This changeset lowers the font-weight value from `600` to `400` for labels located in the Settings screens.
This is an initial implementation of the WordPress design system, aligning with the broader goal of achieving a more consistent and unified design across the administration.

Props karmatosed, audrasjb.
Fixes #62865.




git-svn-id: https://develop.svn.wordpress.org/trunk@59709 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/css/forms.css

@@ -859,7 +859,7 @@ ul#add-to-blog-users {
 	padding: 20px 10px 20px 0;
 	width: 200px;
 	line-height: 1.3;
-	font-weight: 600;
+	font-weight: 400;
 }
 
 .form-table th.th-full, /* Not used by core. Back-compat for pre-4.8 */