[Test] Remove old non-varlen FA2 test

[MatthewBonanni]

Purpose

This is testing a function that is no longer used anywhere in vLLM, so this PR removes it. This helps eliminate dependence on FA2.

---

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 test_flash_attn_with_paged_kv, a test for the obsolete function flash_attn_with_kvcache. The change is a straightforward code cleanup, removing unused test code. The deletion is self-contained and I found no issues with it.

[LucasWilkinson]

LGTM; can we remove this on the vllm-flash-attn side too?

[MatthewBonanni]

LGTM; can we remove this on the vllm-flash-attn side too?

@LucasWilkinson are you sure? I realized that this still exists on upstream main, removing it would cause a divergence: https://github.com/Dao-AILab/flash-attention

Edit: discussed offline. Created PR: vllm-project/flash-attention#107

[yewentao256]

LGTM, thanks for the work!