* org.el (org-calendar-agenda-action-key): Delete an option.
(org-mode-map): Delete its keybinding.
(org-agenda-action-marker, org-mark-entry-for-agenda-action):
Delete.
* org-agenda.el (org-agenda-diary-entry): Don't prevent from
being used outside of Org agendas, as it can be used in
calendar buffers too.
Note that we may have to reimplement the functions related to
"k" in the calendar.