Remove stale code

swap/src/bitcoin.rs

@@ -233,11 +233,6 @@ pub trait TransactionBlockHeight {
     async fn transaction_block_height(&self, txid: Txid) -> Result<BlockHeight>;
 }
 
-#[async_trait]
-pub trait WaitForBlockHeight {
-    async fn wait_for_block_height(&self, height: BlockHeight);
-}
-
 #[async_trait]
 pub trait GetRawTransaction {
     async fn get_raw_transaction(&self, txid: Txid) -> Result<Transaction>;