Remove the expansion.nix which is useless

Expansion work will be done by yamls fixture

Author: Damon Chen

integration_tests/shell.nix

@@ -19,6 +19,5 @@ pkgs.mkShell {
     (import ../nix/testenv.nix { inherit pkgs; })
     (import ../nix/chainmain.nix { inherit pkgs; })
     (import ../nix/hermes.nix { inherit pkgs; })
-    (import ../nix/expansion.nix { inherit pkgs; })
   ];
 }