[FIX] base_location: all users should be able to read

For some reason, this access was removed during the migration to 12.0 (67baf9196).
But this security is perfectly valid and aligned to Odoo core's security for `res.city`[^1].

Without this, you might get bitten while trying to implement website features that
require reading or setting partner's zip_id.

[^1]: https://github.com/odoo/odoo/blob/f5a5d9616/addons/base_address_city/security/ir.model.access.csv

base_location/security/ir.model.access.csv

@@ -1,2 +1,3 @@
 "id","name","model_id:id","group_id:id","perm_read","perm_write","perm_create","perm_unlink"
+"ir_model_access_cityzip_all","res_city_zip all users","model_res_city_zip",,1,0,0,0
 "ir_model_access_cityzip0","res_city_zip group_user","model_res_city_zip","base.group_partner_manager",1,1,1,1