unify on 2105 now that that's the only one we're using

shell.nix

 let
-  # ourpkgs = import ./nixpkgs-ps.nix { };
   release2105 = import ./nixpkgs-2105.nix { };
 in
 { pkgs ? release2105 }:
@@ -7,7 +6,7 @@ pkgs.mkShell {
   NIX_PATH = "nixpkgs=${pkgs.path}";
   buildInputs = [
     pkgs.morph
-    release2105.vagrant
+    pkgs.vagrant
     pkgs.jp
   ];
 }