Remove manual flush when sending buffer release event

This way we can batch more events before flushing the client connection.

src/wayland/server/buffer_interface.cpp

@@ -238,7 +238,6 @@ void BufferInterface::unref()
     if (d->refCount == 0) {
         if (d->buffer) {
             wl_buffer_send_release(d->buffer);
-            wl_client_flush(wl_resource_get_client(d->buffer));
         }
     }
 }