refactor: refine Windows support and convert use-package :if to conditionals

lisp/init-completion.el

@@ -166,11 +166,11 @@ targets."
   (:map corfu-map
 	("RET" . nil)))
 
-(use-package corfu-terminal
-  :if (not (and (display-graphic-p)
-                (>= emacs-major-version 31)))
-  :hook
-  (after-init . corfu-terminal-mode))
+(if (not (and (display-graphic-p)
+              (>= emacs-major-version 31)))
+    (use-package corfu-terminal
+      :hook
+      (after-init . corfu-terminal-mode)))
 
 (use-package emacs
   :custom