According to https://www.easytax.co/en/countries/greece the vat number format for Greece is EL123456783 instead of GR12345670. We also delete the line for country code `el` from `_ref_vat` dict as we use `gr` for Greece. opw-3845662 closes odoo/odoo#161955 X-original-commit: b97c74e43638d685b2af8ede4940f37b6a5cd031 Signed-off-by: Wala Gauthier (gawa) <gawa@odoo.com> Signed-off-by: Guillaume Vanleynseele (guva) <guva@odoo.com>