[Misc] Remove deprecated VLLM_ALL2ALL_BACKEND environment variable (#33535)

Signed-off-by: carlory <baofa.fan@daocloud.io>
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

tests/kernels/moe/modular_kernel_tools/common.py

@@ -150,10 +150,7 @@ class Config:
             "VLLM_USE_DEEP_GEMM": str(int(self.needs_deep_gemm())),
         }
 
-        backend = self.all2all_backend()
-        vllm_config.parallel_config.all2all_backend = backend
-        if backend is not None:
-            env_dict.update({"VLLM_ALL2ALL_BACKEND": backend})
+        vllm_config.parallel_config.all2all_backend = self.all2all_backend()
 
         if self.fused_moe_chunk_size is not None:
             env_dict.update(