[FIX] account_voucher: Purchase receipt bill date twice in the view

The `account.voucher` field `date` was twice in the view
`view_purchase_receipt_form`

Besides the fact the field was twice in the view,
this prevented to set a date in the past
for the resulting journal entries,
as the second field `date` input of the view
contained the date of today, while
only the first one was visible and editable
by the user, and it was the second field
value which was took into account when
passing the form values to the server,
most-likely because this second field was set
further in the view.

opw-674712

addons/account_voucher/voucher_sales_purchase_view.xml

@@ -220,9 +220,6 @@
                             </group>
                         </page>
                         <page string="Journal Items" attrs="{'invisible': [('state','!=','posted')]}" groups="base.group_no_one">
-                            <group col="4">
-                                <field name="date"/>
-                            </group>
                             <group>
                                 <field name="move_id" readonly="1"/>
                             </group>