opencollada: remove unneeded Apple SDK

Per PR review:

> Our darwin SDK has been reworked, so these frameworks are not needed
> and provide empty dummies.

pkgs/by-name/op/opencollada/package.nix

@@ -1,6 +1,5 @@
 {
   cmake,
-  darwin,
   fetchFromGitHub,
   fetchurl,
   lib,
@@ -47,10 +46,6 @@ stdenv.mkDerivation rec {
     pkg-config
   ];
 
-  buildInputs = lib.optionals stdenv.hostPlatform.isDarwin (
-    with darwin.apple_sdk.frameworks; [ AGL ]
-  );
-
   propagatedBuildInputs = [
     libxml2
     pcre