Update Global Constraint Catalog link

Author: Mikael Zayenz Lagerkvist

index.html

@@ -22,7 +22,7 @@ <h2>Gecode</h2>
       level of efficiency as the variables that come predefined with Gecode.</dd>
 
   <dt>comprehensive</dt>
-  <dd>Gecode has a comprehensive set of features: constraints over integers, Booleans, sets, and floats (it implements more than 70 constraints from the <a href="https://www.emn.fr/z-info/sdemasse/gccat/">Global Constraint Catalog</a> and many more on top); C++ modeling layer; advanced branching heuristics (accumulated failure count, activity); many search engines (parallel, interactive graphical, restarts); automatic symmetry breaking (LDSB); no-goods from restarts; MiniZinc support; and many more.
+  <dd>Gecode has a comprehensive set of features: constraints over integers, Booleans, sets, and floats (it implements more than 70 constraints from the <a href="https://sofdem.github.io/gccat/">Global Constraint Catalog</a> and many more on top); C++ modeling layer; advanced branching heuristics (accumulated failure count, activity); many search engines (parallel, interactive graphical, restarts); automatic symmetry breaking (LDSB); no-goods from restarts; MiniZinc support; and many more.
   </dd>
   <dt>efficient</dt>
   <dd>Gecode offers excellent performance with respect to both runtime and