[FIX] survey: fix add missing field 'comment field as an answer'

The field that adds an option in the MCQ was wrongly removed from the views in
v15.3 in Task-2600241.

This commit fixes it by adding it back with the label 'Comment is an answer'.

taskID-3074257

closes odoo/odoo#106826

X-original-commit: e1fcfddb065b6476a539c640859fc1b5d2e4a68d
Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>