Make the transaction size check more flexible

lightning/src/ln/functional_tests.rs

@@ -285,7 +285,7 @@ fn test_splice_in_simple() {
 	// Check that signed splice funding transaction has been broadcasted
 	assert_eq!(chanmon_cfgs[0].tx_broadcaster.txn_broadcasted.lock().unwrap().len(), 2);
 	let broadcasted_splice_tx = chanmon_cfgs[0].tx_broadcaster.txn_broadcasted.lock().unwrap()[1].clone();
-	assert_eq!(broadcasted_splice_tx.encode().len(), 314);
+	assert!(broadcasted_splice_tx.encode().len() >= 314 && broadcasted_splice_tx.encode().len() <= 315);
 	assert_eq!(broadcasted_splice_tx.txid(), splice_tx.txid());
 	assert_ne!(broadcasted_splice_tx.encode(), splice_tx.encode());