ci: Update the default Python version to 3.11

Signed-off-by: Leandro Lucarella <[email protected]>

Author: llucax

.github/workflows/ci.yaml

@@ -3,7 +3,7 @@ name: frequenz-channels-python
 on: [pull_request, push, workflow_dispatch]
 
 env:
-  DEFAULT_PYTHON_VERSION: "3.10"
+  DEFAULT_PYTHON_VERSION: "3.11"
 
 jobs:
   test: