[FIX] base_address_city: avoid showing city and city_id field together

Before this commit, when the city_id field was set and then removed,
both city and city_id were shown, you would see 2 city fields in a weird
way.

opw-2312641

closes odoo/odoo#56896

X-original-commit: b381fb0b644cf3c94e798319ceecf5d6b97df9ad
Signed-off-by: Nicolas Lempereur (nle) <nle@odoo.com>
Signed-off-by: Jorge Pinna Puissant (jpp) <jpp@odoo.com>

addons/base_address_city/models/res_partner.py

@@ -19,6 +19,10 @@ class Partner(models.Model):
             self.city = self.city_id.name
             self.zip = self.city_id.zipcode
             self.state_id = self.city_id.state_id
+        else:
+            self.city = False
+            self.zip = False
+            self.state_id = False
 
     @api.model
     def _fields_view_get_address(self, arch):