Accessibility: Improve the Site Health accordions.

- removes the definition list and uses the markup from the ARIA Authoring Practices example
- removes incorrect ARIA roles
- avoids ARIA landmark regions proliferation

Props mukesh27 for the initial patch.
Fixes #46714.

Built from https://develop.svn.wordpress.org/trunk@45087


git-svn-id: http://core.svn.wordpress.org/trunk@44896 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/css/site-health-rtl.css

@@ -271,12 +271,16 @@
 	border: 1px solid #e2e4e7;
 }
 
-.health-check-accordion dt {
-	font-weight: 600;
+.health-check-accordion-heading {
+	margin: 0;
 	border-top: 1px solid #e2e4e7;
+	font-size: inherit;
+	line-height: inherit;
+	font-weight: 600;
+	color: inherit;
 }
 
-.health-check-accordion dt:first-child {
+.health-check-accordion-heading:first-child {
 	border-top: none;
 }
 

wp-admin/css/site-health.css

@@ -271,12 +271,16 @@
 	border: 1px solid #e2e4e7;
 }
 
-.health-check-accordion dt {
-	font-weight: 600;
+.health-check-accordion-heading {
+	margin: 0;
 	border-top: 1px solid #e2e4e7;
+	font-size: inherit;
+	line-height: inherit;
+	font-weight: 600;
+	color: inherit;
 }
 
-.health-check-accordion dt:first-child {
+.health-check-accordion-heading:first-child {
 	border-top: none;
 }