[css-display] Remove the ToC number from #privsec.

Author: tabatkins

css-display-3/Overview.bs

@@ -1260,7 +1260,7 @@ Changes</h2>
 			that are intended to accomplish this purpose.)
 	</ul>
 
-Privacy and Security Considerations {#priv-sec}
-===============================================
+<h2 id="priv-sec" class="no-num">
+Privacy and Security Considerations</h2>
 
 This specification introduces no new privacy or security considerations.