[FIX] website_form: binary field do not need _filename
[FIX] website_form: binary field do not need _filename

When a binary field is added to studio, the system will try to write the
name to {binary_field_name}_filename: this works if the field was
created with studio but could not work eg. if just a binary field is
created manually.

opw-2191873
closes #45994

closes odoo/odoo#46164

X-original-commit: 13b65d878d5240f07b279045e30d53915d176a61
Signed-off-by: Nicolas Lempereur (nle) <2907e499a003d1c3ab7944c0a40c6df46e3e3c2f@odoo.com>

ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo