[ONNX] Fix `check_training_mode` in symbolic_helper (#78376)
`check_training_mode` always warned that an op is set to training because it was comparing an int `op_train_mode` with an Enum `GLOBALS.training_mode`. This PR fixes the behavior.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/78376
Approved by: https://github.com/garymm
