eth/channel: Don't set GasPrice in ContractBackend.NewTransactor

Setting TransactOpts.GasPrice forces the transactions to be sent as a
legacy transaction, instead of a type 2 EIP1559, which results in much
higher gas costs.

Also remove the SuggestedGasPrice method from the SimulatedBackend, as
it is not used anymore, because EIP1559 TXs are now sent everywhere.

Signed-off-by: Sebastian Stammler <seb@perun.network>

Author: sebastianst

backend/ethereum/channel/contractbackend.go

@@ -145,11 +145,6 @@ func (c *ContractBackend) NewTransactor(ctx context.Context, gasLimit uint64,
 		return nil, errors.WithMessage(err, "creating transactor")
 	}
 
-	auth.GasPrice, err = c.SuggestGasPrice(ctx)
-	if err != nil {
-		return nil, errors.Wrapf(err, "estimating gas price")
-	}
-
 	auth.GasLimit = gasLimit
 	auth.Context = ctx
 

backend/ethereum/channel/test/simulated.go

@@ -106,11 +106,6 @@ func NewSimulatedBackend(opts ...SimBackendOpt) *SimulatedBackend {
 	return sb
 }
 
-// SuggestGasPrice always returns `GasPrice`.
-func (*SimulatedBackend) SuggestGasPrice(context.Context) (*big.Int, error) {
-	return big.NewInt(GasPrice), nil
-}
-
 // SendTransaction executes a transaction.
 func (s *SimulatedBackend) SendTransaction(ctx context.Context, tx *types.Transaction) error {
 	if err := s.SimulatedBackend.SendTransaction(ctx, tx); err != nil {