build(nix): remove image/postgres

This used a flake output from lockpad and passed it through. It is
preventing builds and is not a critical package at this point in time.

Author: justinrubek

containers/default.nix

@@ -55,8 +55,6 @@
       };
 
       "image/conduit" = inputs'.conduit.packages."image/conduit";
-
-      "image/postgres" = inputs'.lockpad.packages."postgres/docker";
     };
   };
 }