Add codeowners for onnx export (#54287)
Summary:
cc neginraoof spandantiwari SplitInfinity for review
Pull Request resolved: https://github.com/pytorch/pytorch/pull/54287
Reviewed By: zou3519
Differential Revision: D27190058
Pulled By: SplitInfinity
fbshipit-source-id: 2f218e6da563be19338531e57fe8138f530cb86d
