org-table: Do not look after CONSTANTS in Orgtbl mode

* lisp/org-table.el (orgtbl-ctrl-c-ctrl-c): Do not set constants.

Orgtbl provides limited support for Org tables in an arbitrary major
mode.  Any Org syntax outside tables, including keywords, cannot be
supported in this environment.  Therefore there is no point to look
for CONSTANTS keywords.  Moreover, constants can be defined within the
table.

This change allows to move `org-table-set-constants' feature to
`org-set-regexps-and-options' and treat CONSTANTS keyword like any
other keyword (e.g., defining it in a SETUPFILE).

lisp/org-table.el

@@ -4372,7 +4372,6 @@ With prefix arg, also recompute table."
       (when (orgtbl-send-table 'maybe)
 	(run-hooks 'orgtbl-after-send-table-hook)))
      ((eq action 'recalc)
-      (org-table-set-constants)
       (save-excursion
 	(beginning-of-line 1)
 	(skip-chars-backward " \r\n\t")