[Wrong Code Comments] In moe.py, there are two wrong code comments

[xiaodathereal]

The following two comments seem wrong, they need to be switched.

https://github.com/tensorflow/mesh/blob/4e07d5e7186626dbc56f5a6d63c5dc259f9eb9d8/mesh_tensorflow/transformer/moe.py#L423

https://github.com/tensorflow/mesh/blob/4e07d5e7186626dbc56f5a6d63c5dc259f9eb9d8/mesh_tensorflow/transformer/moe.py#L434