Remove the passing of nix cache creds.

There is no way to include them when fetching from a substituter.

docker/server/Dockerfile

@@ -10,8 +10,6 @@ filter-syscalls = false
 substituters = http://ncps.nix-pull-through-cache.svc.cluster.local:80 https://cache.nixos.org
 EOF
 
-# RUN --mount=type=secret,id=cache_token echo "extra-access-tokens = ncps.nix-pull-through-cache.svc.cluster.local=PAT:$(cat /run/secrets/cache_token)" >> /etc/nix/nix.conf
-
 RUN cp "$(nix build nixpkgs#cacert --print-out-paths)/etc/ssl/certs/ca-bundle.crt" /tmp/ca-bundle.crt
 
 COPY . /tmp/build