Fix Qwen3 MoE: also guard EP all-reduce with not use_reduce_scatter (follow-up to #23731)#23734

ByronHsu merged 1 commit intosgl-project:mainsgl-project/sglang:mainfrom

ByronHsu:fix/qwen3-moe-ep-use-reduce-scatter-guardByronHsu/sglang:fix/qwen3-moe-ep-use-reduce-scatter-guardCopy head branch name to clipboard