Fix the link to rss in the blog post footer (#235)

Should be rss.xml instead of feed.xml

Author: Mariatta

src/layouts/PostSingle.astro

@@ -100,7 +100,7 @@ const { title, description, authors, categories, image, date, tags } =
             <p>Don’t miss a beat! Follow us for announcements and updates.</p>
             <ul>
               <li><strong>Blog</strong>: <a href="https://conference.pyladies.com/blog">conference.pyladies.com/blog</a></li>
-              <li><strong>RSS Feed</strong>: <a href="https://conference.pyladies.com/rss.xml">conference.pyladies.com/feed.xml</a></li>
+              <li><strong>RSS Feed</strong>: <a href="https://conference.pyladies.com/rss.xml">conference.pyladies.com/rss.xml</a></li>
               <li><strong>Social Media</strong>: Find our social media handles at the footer.</li>
               <li><strong>Official Conference Hashtag</strong>: <strong>#PyLadiesCon</strong></li>
             </ul>