Remove 'www' from Stack Overflow URL (mmistakes#2054)

Stack Overflow is no longer including `www` in its URLs.

Author: lucascaton

_includes/author-profile.html

@@ -163,7 +163,7 @@ <h3 class="author__name" itemprop="name">{{ author.name }}</h3>
 
       {% if author.stackoverflow %}
         <li>
-          <a href="https://www.stackoverflow.com/users/{{ author.stackoverflow }}" itemprop="sameAs" rel="nofollow noopener noreferrer">
+          <a href="https://stackoverflow.com/users/{{ author.stackoverflow }}" itemprop="sameAs" rel="nofollow noopener noreferrer">
             <i class="fab fa-fw fa-stack-overflow" aria-hidden="true"></i> Stack Overflow
           </a>
         </li>