Revert "Fix MoE backend selection for LoRA (unquantized MoE)" (#40273)

[vllm-agent]

Revert of #40273

This reverts commit d1135a5 (merge commit for PR #40273).

Original PR: #40273
Reason: 1 new CI failure linked to this PR in build #62026:

• Kernels FusedMoE Layer Test (2 H100s) — test_moe_layer parallel test failed with 1/148 subtests failing (subtest 222-2048-2048-64-6-bfloat16-None-True-False-True-False-False-allgather_reducescatter-1-1-2)

The PR changed vllm/model_executor/layers/fused_moe/oracle/unquantized.py which affects MoE backend selection and is a likely root cause for the MoE layer test regression.

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[gemini-code-assist]

Code Review

This pull request removes the logic that previously forced the Triton backend for unquantized MoE when LoRA is enabled. Along with this change, several related test cases and a platform-specific skip marker were removed from the test suite. I have no feedback to provide as there were no review comments to evaluate.