[FIX] base: make ZIP not required for ecuador

In Ecuador, the ZIP code is not a required field to create invoices.
Customers usually don't even know their ZIP code as the street number,
city and state (province) are mostly used for delivery (and not the
ZIP code).

task-3585823

Part-of: odoo/odoo#142730

odoo/addons/base/data/res_country_data.xml

@@ -411,6 +411,7 @@
             <field name="currency_id" ref="USD" />
             <field eval="593" name="phone_code" />
             <field name="vat_label">RUC</field>
+            <field name='zip_required'>0</field>
         </record>
         <record id="ee" model="res.country">
             <field name="name">Estonia</field>