PaymentRequest: remove deprecated card issuer network as payment method

[dandv]

https://googlechrome.github.io/samples/paymentrequest/credit-cards/ shows the following warning in the console:

[Deprecation] Card issuer network ("amex", "diners", "discover", "jcb", "mastercard", "mir", "unionpay", "visa") as payment method is deprecated and will be removed in M64, around January 2018. Please use payment method name "basic-card" with issuer network in the "supportedNetworks" field instead. See https://www.chromestatus.com/features/5725727580225536 for more details.

[TwitRco]

Duplicate of #