[FIX] mail: open livechat session page in non-debug

The session page could not be open in non-debug
due to create_date being restricted to debug.
This field is required for ordering of records.

There was no reason to restrict to just have it
only in debug, so we just make it available at
any time.

closes odoo/odoo#106535

Signed-off-by: Sébastien Theys (seb) <seb@odoo.com>