[CI/Build] Remove redundant LoRA model tests

[jeejeelee]

Purpose

Since llama and chatglm models can test all LoRA layers, remove the LoRA tests for baichuan and phi2 to reduce CI pressure

Test Plan

Test Result

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Essential Elements of an Effective PR Description Checklist

• The purpose of the PR, such as "Fix some issue (link existing issues this PR will resolve)".
• The test plan, such as providing test command.
• The test results, such as pasting the results comparison before and after, or e2e results
• (Optional) The necessary documentation update, such as updating supported_models.md and examples for a new model.
• (Optional) Release notes update. If your change is user facing, please update the release notes draft in the Google Doc.

[gemini-code-assist]

Code Review

This pull request removes redundant LoRA model tests for baichuan and phi2 to reduce CI pressure. The changes are straightforward, involving the deletion of two test files and a related test fixture. The changes align with the stated purpose. I've identified one minor issue: an unused test fixture for baichuan that was left behind. Removing it would complete the cleanup. Overall, this is a good change for optimizing the CI process.