remove unused

Author: enriquesouza

rust/tw_cosmos_sdk/src/modules/tx_builder.rs

@@ -9,7 +9,6 @@ use crate::public_key::{CosmosPublicKey, PublicKeyParams};
 use crate::transaction::message::cosmos_generic_message::JsonRawMessage;
 use crate::transaction::message::{CosmosMessage, CosmosMessageBox};
 use crate::transaction::{Coin, Fee, SignMode, SignerInfo, TxBody, UnsignedTransaction};
-use std::borrow::Cow;
 use std::marker::PhantomData;
 use std::str::FromStr;
 use tw_coin_entry::coin_context::CoinContext;