Fix electrum warnings.

Author: arik-so

lightning-transaction-sync/src/electrum.rs

@@ -99,7 +99,7 @@ where
 		while let Some(_) = self.client.block_headers_pop()? {}
 
 		let tip_notification = self.client.block_headers_subscribe()?;
-		let mut tip_header = tip_notification.header;
+		let tip_header = tip_notification.header;
 		let mut tip_height = tip_notification.height as u32;
 
 		loop {
@@ -524,7 +524,7 @@ where
 	fn get_confirmed_tx(
 		&self, tx: &Transaction, prob_conf_height: u32,
 	) -> Result<ConfirmedTx, InternalError> {
-		let txid = tx.txid();
+		let txid = tx.compute_txid();
 		match self.client.transaction_get_merkle(
 			&electrum_client::bitcoin::Txid::from_slice(txid.as_ref()).unwrap(),
 			prob_conf_height as usize,