Merge branch 'feature/dune-module-3.4-version' into 'releases/3.4'

[dune.module][release/3.4] Fix version to stable version number

See merge request !2648

dune.module

 Module: dumux
-Version: 3.4-git
+Version: 3.4
 Author: The DuMux Team
 Maintainer: dumux@listserv.uni-stuttgart.de
 Depends: dune-common (>= 2.7) dune-grid (>= 2.7) dune-localfunctions (>= 2.7) dune-istl (>= 2.7)