Fixed link to MiniZinc

The old one didn't work anymore.

Author: HelgeS

interfaces.html

@@ -11,7 +11,7 @@
   <ul>
   <li><a href="/flatzinc.html">FlatZinc/Gecode</a><br />
 	<i>provides a parser for the
-	  <a href="http://www.g12.cs.mu.oz.au/minizinc/">FlatZinc modelling 
+	  <a href="https://www.minizinc.org/">FlatZinc modelling 
 	    language</a>.</i>
   </li>
   </ul>
@@ -84,4 +84,4 @@
 
   <p>If you are developing an interface for Gecode and would like it to be listed
   here, please send us an email.</p>
-  
+