zfsLegacyCrypto: remove

This package was only mandatory for migration for people on zfsUnstable
in nixos unstable.

nixos/modules/tasks/filesystems/zfs.nix

@@ -23,11 +23,7 @@ let
 
   kernel = config.boot.kernelPackages;
 
-  packages = if config.boot.zfs.enableLegacyCrypto then {
-    spl = kernel.splLegacyCrypto;
-    zfs = kernel.zfsLegacyCrypto;
-    zfsUser = pkgs.zfsLegacyCrypto;
-  } else if config.boot.zfs.enableUnstable then {
+  packages = if config.boot.zfs.enableUnstable then {
     spl = kernel.splUnstable;
     zfs = kernel.zfsUnstable;
     zfsUser = pkgs.zfsUnstable;
@@ -117,27 +113,6 @@ in
           '';
       };
 
-      enableLegacyCrypto = mkOption {
-        type = types.bool;
-        default = false;
-        description = ''
-          Enabling this option will allow you to continue to use the old format for
-          encrypted datasets. With the inclusion of stability patches the format of
-          encrypted datasets has changed. They can still be accessed and mounted but
-          in read-only mode mounted. It is highly recommended to convert them to
-          the new format.
-
-          This option is only for convenience to people that cannot convert their
-          datasets to the new format yet and it will be removed in due time.
-
-          For migration strategies from old format to this new one, check the Wiki:
-          https://nixos.wiki/wiki/NixOS_on_ZFS#Encrypted_Dataset_Format_Change
-
-          See https://github.com/zfsonlinux/zfs/pull/6864 for more details about
-          the stability patches.
-          '';
-      };
-
       extraPools = mkOption {
         type = types.listOf types.str;
         default = [];