[staging-next] awscli2: fix urllib3 override (#434786)

pkgs/by-name/aw/awscli2/package.nix

···
           build-system = with final; [
             setuptools
           ];
+          postPatch = null;
           src = prev.src.override {
             inherit version;
             hash = "sha256-+OzBu6VmdBNFfFKauVW/jGe0XbeZ0VkGYmFxnjKFgKA=";