[Misc] Remove duplicate multiproc method setting for CPU platform (#19649)

Signed-off-by: Isotr0py <2037008807@qq.com>

Author: Isotr0py

vllm/platforms/cpu.py

@@ -216,9 +216,6 @@ def check_and_update_config(cls, vllm_config: VllmConfig) -> None:
         # Disable torch async compiling which won't work with daemonic processes
         os.environ["TORCHINDUCTOR_COMPILE_THREADS"] = "1"
 
-        # Share the cpusets list among ranks by spawning process instead
-        os.environ["VLLM_WORKER_MULTIPROC_METHOD"] = "spawn"
-
         # Intel OpenMP setting
         ld_prealod_str = os.getenv("LD_PRELOAD", "")
         if "libiomp5.so" in ld_prealod_str: