Remove ort pin for gpu ci

[xiaoyu-work]

Describe your changes

Remove ort pin for gpu ci

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.

(Optional) Issue link

[Copilot]

Pull request overview

This PR updates the Azure Pipelines Linux GPU test job template to stop pinning the ONNX Runtime GPU package version, so GPU CI installs the latest stable onnxruntime-gpu available for the configured Python version.

Changes:

• Remove the upper-bound version constraint from the onnxruntime-gpu package spec used by Linux GPU CI.