Update build Python versions to 3.12

.github/workflows/asv_check.yml

@@ -23,7 +23,7 @@ jobs:
       - name: Install Python
         uses: actions/setup-python@v5
         with:
-          python-version: '3.9'
+          python-version: '3.12'
 
       - name: Install asv
         run: pip install asv==0.6.4

.github/workflows/flake8.yml

@@ -7,10 +7,10 @@ jobs:
     steps:
       - name: Checkout source
         uses: actions/checkout@v4
-      - name: Install Python 3.11
+      - name: Install Python 3.12
         uses: actions/setup-python@v5
         with:
-          python-version: '3.11'
+          python-version: '3.12'
       - name: Install Flake8 5.0.4 linter
         run: pip install flake8==5.0.4  # use this version for --diff option
       - name: Setup Flake8 output matcher for PR annotations

.github/workflows/publish.yml

@@ -22,7 +22,7 @@ jobs:
     - name: Set up Python
       uses: actions/setup-python@v5
       with:
-        python-version: 3.9
+        python-version: "3.12"
 
     - name: Install build tools
       run: |

readthedocs.yml

@@ -11,7 +11,7 @@ sphinx:
 build:
    os: ubuntu-lts-latest
    tools:
-     python: "3.11"
+     python: "3.12"
    jobs:
      # fetch the full history so that setuptools_scm can determine the
      # correct version string for long PRs with many commits