Stop C-a and C-e from deactivating the mark

* lisp/org.el (org-beginning-of-line):
(org-end-of-line): Bind deactivate-mark to avoid that this command
deactivates it.

lisp/org.el

@@ -22704,7 +22704,7 @@ beyond the end of the headline."
 	(special (if (consp org-special-ctrl-a/e)
 		     (car org-special-ctrl-a/e)
 		   org-special-ctrl-a/e))
-	refpos)
+	deactivate-mark	refpos)
     (if (org-bound-and-true-p visual-line-mode)
 	(beginning-of-visual-line 1)
       (beginning-of-line 1))
@@ -22772,7 +22772,8 @@ the cursor is already beyond the end of the headline."
 	(move-fun (cond ((org-bound-and-true-p visual-line-mode)
 			 'end-of-visual-line)
 			((fboundp 'move-end-of-line) 'move-end-of-line)
-			(t 'end-of-line))))
+			(t 'end-of-line)))
+	deactivate-mark)
     (if (or (not special) arg) (call-interactively move-fun)
       (let* ((element (save-excursion (beginning-of-line)
 				      (org-element-at-point)))