Remove legend styles and use new paragraph class name

Author: sabernhardt

src/wp-admin/css/forms.css

@@ -1114,15 +1114,7 @@ table.form-table td .updated p {
 	margin-top: 0;
 }
 
-.permalink-structure-optional legend {
-	padding: 0;
-}
-
-.permalink-structure-optional legend + p {
-	margin-top: 0;
-}
-
-.permalink-structure-optional p code {
+.permalink-structure-optional-description code {
 	display: inline-block;
 }