py/stream: Update comment for mp_stream_write_adaptor.

py/stream.c

@@ -242,7 +242,7 @@ mp_obj_t mp_stream_write(mp_obj_t self_in, const void *buf, size_t len, byte fla
     }
 }
 
-// XXX hack
+// This is used to adapt a stream object to an mp_print_t interface
 void mp_stream_write_adaptor(void *self, const char *buf, size_t len) {
     mp_stream_write(MP_OBJ_FROM_PTR(self), buf, len, MP_STREAM_RW_WRITE);
 }