lisp/org.el: (org-save-all-org-buffers): Prevent `org-mode' reload

* lisp/org.el: (org-save-all-org-buffers): Ensure `save-some-buffers' PRED returns boolean.

As of this upstream commit:

https://git.savannah.gnu.org/cgit/emacs.git/commit/?id=a9ad3d477441feefa3bf6107d58281cb64e0e78a

`save-some-buffers' will call its PRED argument if it returns a function.
Since (derived-mode-p 'org-mode) returns the symbol org-mode,
and org-mode is a function, org-mode is reloaded in modified Org
buffers when calling `org-save-all-org-buffers'. Among other
undesirable behavior, this will cause the buffer's visibility to be
reset to its initial visibility.

lisp/org.el

@@ -15366,7 +15366,7 @@ The value is a list, with zero or more of the symbols `effort', `appt',
   "Save all Org buffers without user confirmation."
   (interactive)
   (message "Saving all Org buffers...")
-  (save-some-buffers t (lambda () (derived-mode-p 'org-mode)))
+  (save-some-buffers t (lambda () (and (derived-mode-p 'org-mode) t)))
   (when (featurep 'org-id) (org-id-locations-save))
   (message "Saving all Org buffers... done"))