[dynamo] Disable pytest AST rewriting in test_export (#100484)
pytest rewrites Python assert statements in unit tests to provide more detailed error messages. Unfortunately, this breaks some dynamo tests. Disable AST rewriting in test_export.py so that "pytest test/dynamo/test_export.py" passes.
Fixes #93449
Pull Request resolved: https://github.com/pytorch/pytorch/pull/100484
Approved by: https://github.com/tugsbayasgalan
