refactor: remove redundant sops secret definition

Changed files
-1
systems
-1
systems/koumakan/configuration.nix
···
sops.age.sshKeyPaths = ["/etc/ssh/ssh_host_ed25519_key"];
sops.defaultSopsFile = ../../creds/sops/koumakan.yaml;
-
sops.secrets."synapse.yaml" = {}; # test only
# Just don't change this :p
system.stateVersion = "23.05"; # Did you read the comment?