Downgrade Python 3.11 to work around aiohttp bug

Since python/cpython#98540 which was included in
Python 3.11.1, aiohttp can fail if two tasks are trying to close the
connection concurrently.

.ci/variables.json

@@ -9,7 +9,7 @@
     "PY38": "3.8.16",
     "PY39": "3.9.16",
     "PY310": "3.10.10",
-    "PY311": "3.11.2",
+    "PY311": "3.11.0",
     "MIN_PY_VER": "3.8.13"
   }
 }