Update mismatched end tag for code example in section 'Loops'

jekyll.md

@@ -139,7 +139,7 @@ Markup
 {% for post in site.posts %}
   <a href="{{ post.url }}">
     <h2>{{ post.title }}</h2>
-    <p>{{ post.date | date_to_string }}</h2>
+    <p>{{ post.date | date_to_string }}</p>
   </a>
 {% endfor %}
 ```