bpo-47038: Increase a test timeout for slow CI machines (GH-31951)

(cherry picked from commit a7c54148322781cb0f332d440a3454d550ef6414)

Co-authored-by: Andrew Svetlov <andrew.svetlov@gmail.com>
diff --git a/Lib/test/test_asyncio/test_waitfor.py b/Lib/test/test_asyncio/test_waitfor.py
index 874aabf..45498fa 100644
--- a/Lib/test/test_asyncio/test_waitfor.py
+++ b/Lib/test/test_asyncio/test_waitfor.py
@@ -144,7 +144,7 @@ async def foo():
         self.assertTrue(fut.done())
         # it should have been cancelled due to the timeout
         self.assertTrue(fut.cancelled())
-        self.assertLess(t1 - t0, 0.2)
+        self.assertLess(t1 - t0, 0.5)
         self.assertEqual(foo_running, False)
 
     async def test_wait_for_blocking(self):