Query only valid payments for order confirmation_required?

Prevent a confirmation step in cases where a previous selected payment
method which required confirmation failed and customer picked one that
doesnt require confirmation next

Fixes #3970
Remote erb inline comment from backend/payment_method/form

Motivation is to avoid parse errors when trying to deface that file

See #3913
Bump kaminari to 0.15.0

Conflicts:
	core/spree_core.gemspec