[Extensions Docs] Fix closing tag

s/h2/h3

Bug: None
Change-Id: Ie874f5592b8244a58d0d41659b7b5a94f632a5b3
Reviewed-on: https://chromium-review.googlesource.com/1186924Reviewed-by: Karan Bhatia <karandeepb@chromium.org>
Commit-Queue: Devlin <rdevlin.cronin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#585628}

chrome/common/extensions/docs/templates/articles/inline_faq.html

@@ -53,7 +53,7 @@
 
 <h2 id="after_disabled">After inline-installation is disabled</h2>
 
-<h3 id="future_flow">What will the installation flow look like?</h2>
+<h3 id="future_flow">What will the installation flow look like?</h3>
 
 <p>
   When your site calls <code>chrome.webstore.install()</code>,