fix: downgrade python version for flake8

pyproject-flake8 doesn't support python 3.12

.github/workflows/format.yml

@@ -16,7 +16,7 @@ jobs:
     - uses: actions/checkout@v3
     - uses: actions/setup-python@v4
       with:
-        python-version: 3.12
+        python-version: 3.11
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip