Do not use pytest-asyncio 0.11.0

tests/integration/test_aiopg_connector.py::test_execute_query_simultaneous fails
with pytest-asyncio 0.11.0.

See pytest-dev/pytest-asyncio#154.

setup.cfg

@@ -41,7 +41,7 @@ test =
     pytest-mock
     pytest-cov
     pytest-click
-    pytest-asyncio
+    pytest-asyncio<0.11.0
 
 lint =
     black