Update tests with zero3 for RLOO and GRPO as xfail only with transformers >= v5

[albertvillanova]

Update tests with zero3 for RLOO and GRPO as xfail only with transformers >= v5.

This PR updates the test suite to more accurately handle failures related to ZeRO-3 when using newer versions of the transformers library. Specifically, it refines the test expectations so that tests using ZeRO-3 are only expected to fail when transformers version is 5.0.0 or higher.

I tested locally that the error appeared in transformers v5.0.0 after the merge of:

• add rotary kernel support to Qwen3 model transformers#41147

See investigation in underlying issue:

• RLOO and GRPO failing with ZeRO3: IndexError: pop from an empty deque #4899 (comment)

Changes

Test suite improvements:

• Updated the test_reward and test_rloo test cases in tests/distributed/test_distributed.py to mark ZeRO-3 tests as expected to fail only when transformers version is 5.0.0 or newer, instead of unconditionally. This makes the test results more accurate and prevents false negatives on older versions.

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Note

Low Risk
Low risk: only adjusts pytest xfail conditions for distributed tests, affecting test expectations rather than runtime code paths.

Overview
Updates distributed test parametrizations for test_rloo and test_grpo so the zero3 configuration is marked xfail only when transformers >= 5.0.0 (with strict=True), instead of always expecting failure. This reduces false failures on older transformers versions while retaining the known ZeRO-3 regression coverage.

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