[UI] Remove default override of _payment to allow using ui event

[Jibbarth]

This follow up https://github.com/Sylius/Sylius/pull/13817 and https://github.com/Sylius/PayPalPlugin/pull/276

I noticed that when installing refund plugin on a 1.12 version, I have both Refund functionnality from plugin and the native button under payment.

The refund plugin disable the native button using sylius event, but with this template coming in standard, that has no effect.

Let's remove it, and fully embrace the sylius ui event system :hugs: The paypal customization has been backported in paypal plugin ui events.