tests.fetchtorrent: don't run these tests on Hydra, take 2

As reported in https://github.com/NixOS/nixpkgs/pull/464999#issuecomment-3593574707, I landed this on the wrong attrset and didn't check it.

Now validated with `nix-instantiate --strict  --json --eval -A tests.fetchtorrent.http-link.meta.hydraPlatforms`

pkgs/build-support/fetchtorrent/tests.nix

@@ -29,11 +29,6 @@ let
     '';
     license = lib.licenses.cc-by-30;
     homepage = "https://durian.blender.org/";
-
-    # Reported in https://github.com/NixOS/nixpkgs/pull/458193#issuecomment-3575753211 that these
-    # tests are causing Hydra to spin for hours. They all pass locally, and we don't care too much
-    # about running them on Hydra.
-    hydraPlatforms = [ ];
   };
 
   # Via https://webtorrent.io/free-torrents
@@ -64,10 +59,20 @@ let
     popd
   '';
 
-  # Fixed output derivation hash is identical for all derivations: the empty
-  # directory.
   fetchtorrentWithHash =
-    args: fetchtorrent ({ hash = "sha256-pQpattmS9VmO3ZIQUFn66az8GSmB4IvYhTTCFn6SUmo="; } // args);
+    args:
+    fetchtorrent (
+      {
+        # Fixed output derivation hash is identical for all derivations: the empty directory.
+        hash = "sha256-pQpattmS9VmO3ZIQUFn66az8GSmB4IvYhTTCFn6SUmo=";
+
+        # Reported in https://github.com/NixOS/nixpkgs/pull/458193#issuecomment-3575753211
+        # that these tests are causing Hydra to spin for hours on macOS.
+        # They all pass locally, and we don't care too much about running them on Hydra.
+        meta.hydraPlatforms = [ ];
+      }
+      // args
+    );
 in
 # Seems almost but not quite worth using lib.mapCartesianProduct...
 builtins.mapAttrs (n: v: testers.invalidateFetcherByDrvHash fetchtorrentWithHash v) {