Temporarily remove non-functional homepage example

Author: jberci

web/concepts/templates/index.html

@@ -12,7 +12,7 @@
   <input type="submit" />
   <p>Examples:
     <a href="/concept/circuit/">circuit</a>,
-    <a href="/concept/mathematical%20group/">mathematical group</a>,
+    <!--<a href="/concept/mathematical%20group/">mathematical group</a>,-->
     <a href="/concept/Stone%20duality/">Stone duality</a>,
     <a href="/results/normal">normal</a>
   </p>