mouse: Honor org-checkbox face

* lisp/org-mouse.el: Use org-checkbox rather than bold for checkbox
face for consistent checkbox appearance.

Reported-by: Yaroslav Rogov <rogovyaroslav@gmail.com>
Link: https://orgmode.org/list/A7D22E5B-B1A3-4ADC-9808-121F0D0ECD60@gmail.com

lisp/org-mouse.el

@@ -893,7 +893,7 @@ This means, between the beginning of line and the point."
 		(font-lock-add-keywords
 		 nil
 		 `(("^[ \t]*\\([-+*]\\|[0-9]+[.)]\\) +\\(\\[[ X]\\]\\)"
-		    (2 `(face bold keymap ,org-mouse-map mouse-face highlight) t)))
+		    (2 `(face org-checkbox keymap ,org-mouse-map mouse-face highlight) t)))
 		 t))
 
 	      (defadvice org-open-at-point (around org-mouse-open-at-point activate)