Revert "fish: switch to fetchFromGitHub"
Revert "fish: switch to fetchFromGitHub"

This reverts commit cc997f28d154e6bc47eacbe3632859090fedd616.

I confused the URLs. The files have the same contents but the former URL is recommended by upstream.

NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs