Update customize-package-emacs-version-alist

* lisp/org.el (customize-package-emacs-version-alist): Map Org 9.4 to
Emacs 28.1.

Emacs 27 is nearing release.  A sync of 9.4 would be with the current
version for Emacs's master branch.

lisp/org.el

@@ -4856,7 +4856,8 @@ The following commands are available:
 		   ("9.0" . "26.1")
 		   ("9.1" . "26.1")
 		   ("9.2" . "27.1")
-		   ("9.3" . "27.1")))
+		   ("9.3" . "27.1")
+		   ("9.4" . "28.1")))
 
 (defvar org-mode-transpose-word-syntax-table
   (let ((st (make-syntax-table text-mode-syntax-table)))