Administration: Fix some HTML validation errors.

Fixes some minor HTML issues in the admin and, most notably, changes the rel
attribute used in the List Tables from `rel="permalink"` to `rel="bookmark"`.

Props mihai2u, pento, arena, topher1kenobe, michalzuber, stubgo.
Fixes #37004.

Built from https://develop.svn.wordpress.org/trunk@40823


git-svn-id: http://core.svn.wordpress.org/trunk@40680 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/css/forms-rtl.css

@@ -650,8 +650,10 @@ ul#add-to-blog-users {
 	font-weight: 600;
 }
 
-.form-table th.th-full {
+.form-table th.th-full, /* Not used by core. Back-compat for pre-4.8 */
+.form-table .td-full {
 	width: auto;
+	padding: 20px 0 20px 10px;
 	font-weight: 400;
 }