[local-worker-mgr] Use _get_context() for cpu count, too

Not strictly necessary, but for consistency.

compiler_opt/distributed/local/local_worker_manager.py

@@ -253,7 +253,7 @@ def create_local_worker_pool(worker_cls: 'type[worker.Worker]',
                              **kwargs) -> worker.FixedWorkerPool:
   """Create a local worker pool for worker_cls."""
   if not count:
-    count = multiprocessing.get_context().cpu_count()
+    count = _get_context().cpu_count()
   final_kwargs = worker.get_full_worker_args(worker_cls, **kwargs)
   stubs = [_make_stub(worker_cls, *args, **final_kwargs) for _ in range(count)]
   return worker.FixedWorkerPool(workers=stubs, worker_concurrency=16)