Fix syntax error on Asyncio example in doc (GH-9387) (GH-9388)

The `gather` method requires to close the parenthesis, but it is being closed twice.
(cherry picked from commit 9c53fa6ad9)

Co-authored-by: Miguel Ángel García <magmax@users.noreply.github.com>

Doc/library/asyncio-task.rst

@@ -232,7 +232,7 @@ Running Tasks Concurrently
               factorial("A", 2),
               factorial("B", 3),
               factorial("C", 4),
-          ))
+          )
 
       asyncio.run(main())