Use sops for private key distribution

nixos/modules/borgbackup.nix

@@ -133,7 +133,6 @@ in {
     };
     environment.persistence.${config.impermanence.name} = {
       users.fsaccount.files = [
-        /*
         {
           file = ".ssh/known_hosts";
           parentDirectory = {
@@ -142,8 +141,6 @@ in {
             mode = "u=rwx,g=,o=";
           };
         }
-        */
-        ".ssh/known_hosts"
       ];
     };
     sops.secrets.backupKey = {