org-element--cachy-sync: Add exception for unregistered changes

* lisp/org-element.el (org-element--cache-sync): Another special case
when Emacs <28 silently changes `buffer-chars-modified-tick'.

Fixes https://list.orgmode.org/so53mm$obe$1@ciao.gmane.io/T/#mad982a75885b1eda669d8cf7decee15c3917957b

lisp/org-element.el

@@ -5880,7 +5880,7 @@ updated before current modification are actually submitted."
                                     ;; Note: 4 is a footprint for
                                     ;; (let ((inhibit-modification-hooks t))
                                     ;; (insert "blah"))
-                                    '(1 3 6 7))))
+                                    '(1 3 6 7 8))))
                       (and (boundp 'org-batch-test) org-batch-test))
               (org-element--cache-warn "Unregistered buffer modifications detected. Resetting.
 If this warning appears regularly, please report it to Org mode mailing list (M-x org-submit-bug-report).