[CI] Remove flashinfer cache cleanup to reduce unit test runtime

[EmmonsCurse]

Motivation

The flashinfer cache cleanup step was introducing unnecessary overhead during unit test execution.
Since the cache removal is not required for test correctness, it leads to increased test runtime without providing additional value.

Modifications

• Removed the explicit cleanup of the flashinfer cache directory (/root/.cache/flashinfer) in the distributed test.
• Eliminated subprocess-based cache deletion to streamline test startup and improve overall CI efficiency.

Usage or Command

N/A

Accuracy Tests

N/A

Checklist

• Add at least a tag in the PR title.
  • Tag list: [[FDConfig],[APIServer],[Engine], [Scheduler], [PD Disaggregation], [Executor], [Graph Optimization], [Speculative Decoding], [RL], [Models], [Quantization], [Loader], [OP], [KVCache], [DataProcessor], [BugFix], [Docs], [CI], [Optimization], [Feature], [Benchmark], [Others], [XPU], [HPU], [GCU], [DCU], [Iluvatar], [Metax]]
  • You can add new tags based on the PR content, but the semantics must be clear.
• Format your code, run pre-commit before commit.
• Add unit tests. Please write the reason in this PR if no unit tests.
• Provide accuracy results.
• If the current PR is submitting to the release branch, make sure the PR has been submitted to the develop branch, then cherry-pick it to the release branch with the [Cherry-Pick] PR tag.

[paddle-bot]

Thanks for your contribution!

[EmmonsCurse]

/skip-ci ci_iluvatar
/skip-ci ci_hpu
/skip-ci build_xpu
/skip-ci gpu_4cards_test
/skip-ci stable_test
/skip-ci base_test
/skip-ci logprob_test
/skip-ci pre_ce_test

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
⚠️ Please upload report for BASE (develop@5e866e3). Learn more about missing BASE report.

Additional details and impacted files

@@            Coverage Diff             @@
##             develop    #7476   +/-   ##
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  Coverage           ?   73.85%           
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  Files              ?      398           
  Lines              ?    54988           
  Branches           ?     8616           
==========================================
  Hits               ?    40613           
  Misses             ?    11659           
  Partials           ?     2716           

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[PaddlePaddle-bot]

🤖 AI Code Review | 2026-04-20 23:20:16

📋 Review 摘要

PR 概述：移除分布式测试中不必要的 flashinfer 缓存清理步骤，减少 CI 单元测试运行时间
变更范围：tests/layers/test_trtllm_allreduce_rms_fusion.py
影响面 Tag：CI

问题

未发现阻塞性问题。

总体评价

变更简洁明确，移除了与测试正确性无关的缓存清理操作（rm -rf /root/.cache/flashinfer），可有效减少 CI 测试启动开销。剩余代码中 os 和 subprocess 模块仍有使用，无死导入问题。