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.
Built from https://develop.svn.wordpress.org/trunk@45403


git-svn-id: http://core.svn.wordpress.org/trunk@45214 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/install.php

@@ -113,7 +113,7 @@ function display_setup_form( $error = null ) {
 <p class="message"><?php echo $error; ?></p>
 <?php } ?>
 <form id="setup" method="post" action="install.php?step=2" novalidate="novalidate">
-	<table class="form-table">
+	<table class="form-table" role="presentation">
 		<tr>
 			<th scope="row"><label for="weblog_title"><?php _e( 'Site Title' ); ?></label></th>
 			<td><input name="weblog_title" type="text" id="weblog_title" size="25" value="<?php echo esc_attr( $weblog_title ); ?>" /></td>