fix: Update feed.xml to fix the build error

Author: yunseo-kim

feed.xml

@@ -53,7 +53,7 @@ permalink: /feed.xml
 
     <summary xml:lang="{{ site.active_lang }}">{% include post-summary.html max_length=400 %}</summary>
     <content type="html" xml:lang="{{ site.active_lang }}" src="{{ post_absolute_url }}">
-    {% include post-description.html max_length=400 %}
+    {{ post.description }}
     <![CDATA[
     <em><p>* Mathematical equations and diagrams included in posts may not display properly when viewed with a feed reader.</p></em>
     {{ post.content }}