Revert part of #9982 to be in line with #9925

When creating PR #9982, I undid a line of PR #9925, that was some
cleanups and fixes, so this undoes that damage.

Changed files
+1 -1
nixos
modules
+1 -1
nixos/modules/tasks/encrypted-devices.nix
···
label = mkOption {
default = null;
example = "rootfs";
-
type = types.uniq (types.nullOr types.str);
+
type = types.nullOr types.str;
description = "Label of the unlocked encrypted device. Set <literal>fileSystems.&lt;name?&gt;.device</literal> to <literal>/dev/mapper/&lt;label&gt;</literal> to mount the unlocked device.";
};