[css-display-3] Markup fix

Needed to make specberus and the validator happy. Otherwise they
complain about h2 h1 h3, with the h3 skipping a level from h1.

Author: frivoal

css-display-3/Overview.bs

@@ -75,6 +75,7 @@ spec: svg2;
 .code-and-figure img {
 	background: transparent;
 }
+.order-example a.self-link { display: none; }
 </style>
 
 <h2 id="intro">
@@ -1375,7 +1376,7 @@ Display Order: the 'order' property</h2>
 
 		<pre class="lang-markup">
 		&lt;article class="sale-item">
-			&lt;h1>Computer Starter Kit&lt;/h1>
+			&lt;h3>Computer Starter Kit&lt;/h3>
 			&lt;p>This is the best computer money can buy, if you don’t have much money.
 			&lt;ul>
 				&lt;li>Computer
@@ -1392,7 +1393,7 @@ Display Order: the 'order' property</h2>
 		<figure>
 			<div id="order-example">
 				<img src="images/computer.jpg" alt='You get: a white desktop computer with matching keyboard and monitor.' width="250" height="188">
-				<h1 id=quiet-pubrules-1 style="font-size: 1.4em;">Computer Starter Kit</h1>
+				<h3 class="no-num no-toc" id=quiet-pubrules-1 style="font-size: 1.4em; color: inherit;">Computer Starter Kit</h3>
 				<p>
 					This is the best computer money can buy,
 					if you don't have much money.