[FIX] web: introduce format for many2one_reference

The format of `many2one_reference` was not introduced when the new field type
was created, which leads to errors when the web client is trying to display the
value of such fields.

Since the value of this field is an ID, it is decided to display it like an
integer, which is consistent with previous behavior: the fields that are now
`many2one_reference` are still stored as integer and they were already displayed
as integer before.

closes odoo/odoo#37216

Signed-off-by: Raphael Collet (rco) <rco@openerp.com>

addons/web/static/src/js/fields/field_utils.js

@@ -662,6 +662,7 @@ return {
         integer: formatInteger,
         many2many: formatX2Many,
         many2one: formatMany2one,
+        many2one_reference: formatInteger,
         monetary: formatMonetary,
         one2many: formatX2Many,
         percentage: formatPercentage,