radarr: change sed separator in update script

[andreisergiu98]

Motivation for this change

I just realized that a base64 string can contain / characters and if we also use / as a separator for sed it will most certainly break at some point. So I replaced it with | and also added gnused package to the script just to be safe.

I am sorry I missed that.

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.

[SuperSandro2000]

I am sorry I missed that.

It just an update script. Nothing game breaking.