Set to use dynamo=True only with PyTorch 2.6 temporarily

[justinchuby]

Describe your changes

For the Olive release, in the ONNX export pass, since when dynamo=True the dynamic_shapes argument is not provided properly, we temporarily change the check to require torch 2.6 to enable the new dynamo=True logic pass. This way when a user has torch 2.5 Olive will still use the old dynamo_export logic and function without errors.

Checklist before requesting a review

• Add unit tests for this change.
• Make sure all tests can pass.
• Update documents if necessary.
• Lint and apply fixes to your code by running lintrunner -a
• Is this a user-facing change? If yes, give a description of this change to be included in the release notes.
• Is this PR including examples changes? If yes, please remember to update example documentation in a follow-up PR.

(Optional) Issue link

• [FR]: Supply dynamic_shapes in ONNX export when dynamo=True #1478

[shaahji]

Model exports succeeding.