Accessibility: Make sure layout tables across the admin are correctly linearized.

Adds `role="presentation"` to the `<table>` elements used for layout purposes.

Ideally, HTML tables should be used for tabular data. When tables are used for layout purposes, it's important to remove any native semantics so that assistive technologies can correctly announce the table content in a linearized fashion.

Props greatislander, afercia.
Fixes #46899.

git-svn-id: https://develop.svn.wordpress.org/trunk@45403 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/network/site-settings.php

@@ -111,7 +111,7 @@ if ( ! empty( $messages ) ) {
 <form method="post" action="site-settings.php?action=update-site">
 	<?php wp_nonce_field( 'edit-site' ); ?>
 	<input type="hidden" name="id" value="<?php echo esc_attr( $id ); ?>" />
-	<table class="form-table">
+	<table class="form-table" role="presentation">
 		<?php
 		$blog_prefix = $wpdb->get_blog_prefix( $id );
 		$sql         = "SELECT * FROM {$blog_prefix}options