remove doc for obsolete --no-build-hook flag
remove doc for obsolete --no-build-hook flag

`--no-build-hook` appears to have been removed in 25f32625e2f2a3a1e1b3a3811da82f21c3a3b880
rycee/nix,rycee/nix,NixOS/nix,NixOS/nix,NixOS/nix,rycee/nix,NixOS/nix,rycee/nix,NixOS/nix,rycee/nix