Bluetooth: remove forgotten TODO

It's already done.

Signed-off-by: Jonathan Rico <jonathan.rico@nordicsemi.no>

Author: jori-nordic

subsys/bluetooth/host/conn.c

@@ -1048,7 +1048,6 @@ void bt_conn_tx_processor(void)
 
 	bool last_buf = conn_mtu(conn) >= buf_len;
 
-	/* TODO: add sdu_sent callback on last PDU */
 	if (last_buf) {
 		/* Only pull the callback info from the last buffer.
 		 * We still allocate one TX context per-fragment though.