Fix flake8 complaint.

Author: joshstaiger

stdlib/3/concurrent/futures/process.pyi

@@ -8,7 +8,7 @@ EXTRA_QUEUED_CALLS = ...  # type: Any
 
 class BrokenProcessPool(RuntimeError): ...
 
-if sys.version_info >= (3,6):
+if sys.version_info >= (3, 6):
     class ProcessPoolExecutor(Executor[ProcessPoolExecutor]):
         def __init__(self, max_workers: Optional[int] = ...) -> None: ...