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/checkers/spell/README.org

@@ -174,7 +174,7 @@ the word at point should be spell checked. For example:
   "Return t if point is on a word that should be spell checked.
 
 Return nil if on a link url, markup, html, or references."
-  (let ((faces (doom-enlist (get-text-property (point) 'face))))
+  (let ((faces (ensure-list (get-text-property (point) 'face))))
     (or (and (memq 'font-lock-comment-face faces)
              (memq 'markdown-code-face faces))
         (not (cl-loop with unsafe-faces = '(markdown-reference-face

modules/checkers/spell/autoload/+flyspell.el

@@ -11,7 +11,7 @@
 (defun set-flyspell-predicate! (modes predicate)
   "TODO"
   (declare (indent defun))
-  (dolist (mode (doom-enlist modes) +spell--flyspell-predicate-alist)
+  (dolist (mode (ensure-list modes) +spell--flyspell-predicate-alist)
     (add-to-list '+spell--flyspell-predicate-alist (cons mode predicate))))
 
 ;;;###autoload