refactor!: use x/tx/signing in client.TxConfig (#15822)

testutil/testnet/genesis.go

@@ -1,6 +1,7 @@
 package testnet
 
 import (
+	"context"
 	"encoding/json"
 	"fmt"
 	"strconv"
@@ -140,7 +141,10 @@ func (b *GenesisBuilder) GenTx(privVal secp256k1.PrivKey, val cmttypes.GenesisVa
 	}
 
 	// Generate bytes to be signed.
-	bytesToSign, err := txConf.SignModeHandler().GetSignBytes(
+	bytesToSign, err := authsigning.GetSignBytesAdapter(
+		context.Background(),
+		txConf.TxEncoder(),
+		txConf.SignModeHandler(),
 		signing.SignMode_SIGN_MODE_DIRECT,
 		authsigning.SignerData{
 			ChainID: b.chainID,