org-footnote: Fix void `org-element-cache-reset' symbol error

* lisp/org-footnote.el (org-footnote-section): Fix void
  `org-element-cache-reset' symbol error.
org.el (org-insert-link): Don't remove brackets when they belong to a timestamp in a headline

* org.el (org-insert-link): Don't remove brackets when they
belong to a timestamp in a headline.

Thanks to David Belohrad for spotting this.
Merge branch 'maint'