Use training IR in torchchat export

[tugsbayasgalan]

Export is moving to training IR in the coming weeks, as a result export_for_training will be alias to export in the future. After export switches to training IR, i will replace this call with torch.export.export again.

[pytorch-bot[bot]]

:link: Helpful Links

:test_tube: See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/torchchat/1319

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:x: 2 New Failures

As of commit 055cf7b54974f116c243fe72eb99fdcbb12e1720 with merge base e30aaa06511bf490157544054410c468a6382d0f ():

NEW FAILURES - The following jobs have failed:

* [pull / test-cpu-aoti (aarch64, stories15M)](https://hud.pytorch.org/pr/pytorch/torchchat/1319#32883395140) ([gh](https://github.com/pytorch/torchchat/actions/runs/11804046161/job/32883395140)) `.ci/scripts/check_gibberish: line 31: aspell: command not found` * [pull / test-cpu-aoti (x86_64, stories15M)](https://hud.pytorch.org/pr/pytorch/torchchat/1319#32883394098) ([gh](https://github.com/pytorch/torchchat/actions/runs/11804046161/job/32883394098)) `.ci/scripts/check_gibberish: line 31: aspell: command not found`

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[Jack-Khuu]

Awaiting vision pin to realign, then we'll test if segfault is fixed on pytorch/pytorch

[Jack-Khuu]

Absorbing into https://github.com/pytorch/torchchat/pull/1367