[ONNX] Correct a minor typo in warning (#45187)
Summary:
The warning for batch_norm was mentioning dropout.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/45187
Reviewed By: glaringlee
Differential Revision: D23873215
Pulled By: ezyang
fbshipit-source-id: 1dcc82ad16522215f49b4cd0fc0e357b2094e4f2
