Remove remaining Emacs27+ checks

- Remove remaining `EMACS27+` checks, since the whole codebase is
  assumed to run at version 27 or above now
- Remove `EMACS27+` definition since it's no longer needed

modules/completion/helm/config.el

@@ -96,10 +96,7 @@ Can be negative.")
     ;; `completion-styles', since that would be overly intrusive. E.g., it
     ;; results in `company-capf' returning far to many completion candidates.
     ;; Instead, append those styles so that they act as a fallback.
-    (add-to-list 'completion-styles
-                 (if EMACS27+
-                     (if fuzzy 'flex 'helm)
-                   (if fuzzy 'helm-flex 'helm)) t))
+    (add-to-list 'completion-styles (if fuzzy 'flex 'helm) t))
   :config
   (set-popup-rule! "^\\*helm" :vslot -100 :size 0.22 :ttl nil)