nixosTest: Fix invocation

toFunction isn't quite the same as callPackage, but the difference
should only be relevant for cross pkgs, which are generally not
testable anyway.

pkgs/top-level/all-packages.nix

@@ -33612,9 +33612,7 @@ with pkgs;
           loadedTest = if builtins.typeOf test == "path"
             then import test
             else test;
-          calledTest = if lib.isFunction loadedTest
-            then loadedTest { inherit pkgs lib; }
-            else loadedTest;
+          calledTest = lib.toFunction loadedTest pkgs;
         in
           nixosTesting.makeTest calledTest;