refactor: replace doom-enlist with ensure-list

doom-enlist is now a deprecated alias for ensure-list, which is built
into Emacs 28.1+ and is its drop-in replacement. We've already
backported it for 27.x users in doom-lib (in 4bf4978).

Ref: 4bf49785fd

modules/tools/lookup/autoload/docsets.el

@@ -27,7 +27,7 @@ Example:
 Used by `+lookup/in-docsets' and `+lookup/documentation'."
   (declare (indent defun))
   (let ((action (if (keywordp (car docsets)) (pop docsets))))
-    (dolist (mode (doom-enlist modes))
+    (dolist (mode (ensure-list modes))
       (let ((hook (intern (format "%s-hook" mode)))
             (fn (intern (format "+lookup-init--%s-%s" (or action "set") mode))))
         (if (null docsets)