Use sys.executable to find python command.

sdks/python/apache_beam/ml/inference/vllm_inference.py

@@ -24,6 +24,7 @@
 import threading
 import time
 import uuid
+import sys
 from dataclasses import dataclass
 from typing import Any
 from typing import Dict
@@ -118,7 +119,7 @@ def __init__(self, model_name: str, vllm_server_kwargs: Dict[str, str]):
   def start_server(self, retries=3):
     if not self._server_started:
       server_cmd = [
-          'python',
+          sys.executable,
           '-m',
           'vllm.entrypoints.openai.api_server',
           '--model',