Update Doc/howto/a-conceptual-overview-of-asyncio.rst

Co-authored-by: Peter Bierma <zintensitydev@gmail.com>

Author: anordin95

Doc/howto/a-conceptual-overview-of-asyncio.rst

@@ -276,7 +276,7 @@ In this case, that's back to ``... = coroutine.send(None)`` on line 16.
 The coroutine is resumed via the ``coroutine.send(42)`` call on line 21.
 The coroutine picks back up from where it ``yield``\ ed (or paused) on line 3
 and executes the remaining statements in its body.
-When a coroutine finishes it raises a :exc:`StopIteration` exception with the
+When a coroutine finishes, it raises a :exc:`StopIteration` exception with the
 return value attached to the exception.
 
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