Proper heading for admin screens.

First step towards restoring a good heading structure in wp-admin.
The previous `<h1>` contained the site title and a link to the front page and was removed with the toolbar refactoring in 3.2.

Props joedolson, afercia.
Fixes #31650.



git-svn-id: https://develop.svn.wordpress.org/trunk@32974 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/plugin-editor.php

@@ -28,7 +28,7 @@ if ( empty( $plugins ) ) {
 	include( ABSPATH . 'wp-admin/admin-header.php' );
 	?>
 	<div class="wrap">
-		<h2><?php echo esc_html( $title ); ?></h2>
+		<h1><?php echo esc_html( $title ); ?></h1>
 		<div id="message" class="error"><p><?php _e( 'You do not appear to have any plugins available at this time.' ); ?></p></div>
 	</div>
 	<?php
@@ -174,7 +174,7 @@ default:
 </div>
 <?php endif; ?>
 <div class="wrap">
-<h2><?php echo esc_html( $title ); ?></h2>
+<h1><?php echo esc_html( $title ); ?></h1>
 
 <div class="fileedit-sub">
 <div class="alignleft">