Revert "bpo-34037, asyncio: add BaseEventLoop.wait_executor_on_close (GH-13786)" (#13802)

This reverts commit 0f0a30f4da4b529e0f7df857b9f575b231b32758.
diff --git a/Lib/asyncio/base_events.py b/Lib/asyncio/base_events.py
index b1a7f88..e002539 100644
--- a/Lib/asyncio/base_events.py
+++ b/Lib/asyncio/base_events.py
@@ -380,8 +380,6 @@
 class BaseEventLoop(events.AbstractEventLoop):
 
     def __init__(self):
-        # If true, close() waits for the default executor to finish
-        self.wait_executor_on_close = True
         self._timer_cancelled_count = 0
         self._closed = False
         self._stopping = False
@@ -637,7 +635,7 @@
         executor = self._default_executor
         if executor is not None:
             self._default_executor = None
-            executor.shutdown(wait=self.wait_executor_on_close)
+            executor.shutdown(wait=False)
 
     def is_closed(self):
         """Returns True if the event loop was closed."""