update doc and use P2P=LOC for brittle grpo test (#2649)

* update doc and skip brittle grpo test

* fix the path to run the multigpu tests

* increase timeout, use LOC instead of NVL

* typo

* use hf cache from s3 backed cloudfront

* mark grpo as flaky test dues to vllm start

.github/workflows/multi-gpu-e2e.yml

@@ -3,7 +3,7 @@ name: docker-multigpu-tests-biweekly
 on:
   pull_request:
     paths:
-      - 'tests/e2e/multigpu/*.py'
+      - 'tests/e2e/multigpu/**.py'
       - 'requirements.txt'
       - 'setup.py'
       - 'pyproject.toml'