wasm: remove alias to unbreak the channel

Nixpkgs' channel currently can't move forward so long as there is a
trace in evaluating the top-level arguments. Which means that it isn't
possible to add a warning message to warn users of future package
removal.

So the only way forward appears to be just removing the alias
altogether.

(cherry picked from commit b4133ebc17c2742a76d912f4f0bf46719bc7800e)