[3.6] Increate test timeout to satisfy slow CI box (#4236)

(cherry picked from commit 3cf4104)

Co-authored-by: Andrew Svetlov <andrew.svetlov@gmail.com>

tests/test_web_websocket_functional.py

@@ -293,7 +293,7 @@ async def handler(request):
     await asyncio.sleep(0.08, loop=loop)
     assert (await aborted)
 
-    assert elapsed < 0.201, \
+    assert elapsed < 0.25, \
         'close() should have returned before ' \
         'at most 2x timeout.'