helm-docs: remove default platform

pkgs/applications/networking/cluster/helm-docs/default.nix

···
   meta = with lib; {
     homepage = "https://github.com/norwoodj/helm-docs";
     description = "A tool for automatically generating markdown documentation for Helm charts";
-    platforms = platforms.unix;
     license = licenses.gpl3Only;
     maintainers = with maintainers; [ sagikazarmark ];
   };