This commit upgrades the protobuf version. Compared to the previous
v1.2.0 it generates smaller diffs in generated code. This change was
introduced in:
fffb0f7828
This fixes a bug where the RHashStr field on the PaymentHash request for
SubscribeSingleInvoice was being ignored. This replaces the PaymentHash
message for the SubscribeSingleInvoice request with a new message called
SubscribeSingleInvoiceRequest that contains only the RHash field.