[Fix] Update mailing lists addresses.

(cherry picked from commit 2eae1823)
Signed-off-by: Ansgar Burchardt <Ansgar.Burchardt@tu-dresden.de>

dune.module

 Module: dune-istl
 Version: 2.5.1-git
-Maintainer: dune-devel@dune-project.org
+Maintainer: dune-devel@lists.dune-project.org
 Depends: dune-common (>= 2.5.0)
 Whitespace-Hook: Yes