Update concurrent.futures.rst

Author: picnixz

Doc/library/concurrent.futures.rst

@@ -151,10 +151,10 @@ And::
        print(f.result())
 
    executor = ThreadPoolExecutor(max_workers=1)
-   executor.submit(wait_on_future)
-   # Note: calling future.result() here would cause a deadlock because the single
-   # worker thread is already executing wait_on_future(), which itself is waiting
-   # for a result from the same executor.
+   future = executor.submit(wait_on_future)
+   # Note: calling future.result() would also cause a deadlock because
+   # the single worker thread is already waiting for wait_on_future().
+
 
 .. class:: ThreadPoolExecutor(max_workers=None, thread_name_prefix='', initializer=None, initargs=())