nixos/redmine: Drop darcs integration

darcs support was dropped with Redmine 4.0.0. Thus, drop the darcs
integration.

For more information, see https://www.redmine.org/issues/26391.

Signed-off-by: Felix Singer <felixsinger@posteo.net>

nixos/modules/services/misc/redmine.nix

@@ -234,7 +234,6 @@ in
         scm_git_command = "${pkgs.git}/bin/git";
         scm_cvs_command = "${pkgs.cvs}/bin/cvs";
         scm_bazaar_command = "${pkgs.breezy}/bin/bzr";
-        scm_darcs_command = "${pkgs.darcs}/bin/darcs";
       };
     };
 
@@ -299,7 +298,6 @@ in
         imagemagick
         breezy
         cvs
-        darcs
         git
         mercurial
         subversion