[FIX] payment_paypal: fields.Datetime
[FIX] payment_paypal: fields.Datetime

Obviously, it should be `fields.Datetime`, although it luckily works
with `fields.datetime.now()`.

opw-693574

dfang/odoo,dfang/odoo,hip-odoo/odoo,dfang/odoo,hip-odoo/odoo,hip-odoo/odoo,dfang/odoo,ygol/odoo,ygol/odoo,hip-odoo/odoo,hip-odoo/odoo,hip-odoo/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,dfang/odoo,dfang/odoo,ygol/odoo