lib.mkRemovedOptionModule: Show replacement for option usage too

Previously mkRemovedOptionModule would only show the replacement
instructions when the removed option was *defined*. With this change, it
also does so when an option is *used*.

This is essential for options that are only intended to be used such as
`security.acme.directory`, whose replacement instructions would never
trigger without this change because almost everybody only uses the
option and isn't defining it.

lib/modules.nix

@@ -591,6 +591,7 @@ rec {
     { options, ... }:
     { options = setAttrByPath optionName (mkOption {
         visible = false;
+        apply = x: throw "The option `${showOption optionName}' can no longer be used since it's been removed. ${replacementInstructions}";
       });
       config.warnings =
         let opt = getAttrFromPath optionName options; in