Update header format

Author: khushalsagar

css-view-transitions-1/Overview.bs

@@ -1193,7 +1193,7 @@ urlPrefix: https://wicg.github.io/navigation-api/; type: interface;
 
 This specification introduces no new privacy considerations.
 
-<h3 id="sec" class="no-num">Security Considerations</h2>
+<h2 id="sec" class="no-num">Security Considerations</h2>
 
 The images generated using [=capture the image=] algorithm could contain cross-origin data (if the Document is embedding cross-origin resources) or sensitive information like visited links.
 The implementations must ensure this data can not be accessed by the Document.