remove ourselves from the local cabal project file

I do not know why.

flake.nix

@@ -88,7 +88,6 @@
               -- This file is auto-generated by the flake devShell's shellHook.  Do
               -- not edit this file.  Make changes in flake.nix.
               packages:
-                .
                 -- These aren't released on hackage yet so we have to get them
                 -- another way.  Here, we get them from the Nix store.
                 -- tahoe-chk