update GitHub workflows to Python 3.14, drop support for 3.8 and 3.9

* Python 3.9 reached end of life in 2025

Signed-off-by: Armin Tänzer <armin.taenzer@tngtech.com>

Author: armintaenzertng

.github/workflows/check_codestyle.yml

@@ -20,7 +20,7 @@ jobs:
     strategy:
       matrix:
         os: [ ubuntu-latest, macos-latest, windows-latest ]
-        python-version: [ "3.8", "3.9", "3.10", "3.11" ]
+        python-version: [ "3.14" ]
 
     steps:
       - uses: actions/checkout@v3

.github/workflows/docs.yml

@@ -19,7 +19,7 @@ jobs:
       - name: Setup Python
         uses: actions/setup-python@v4
         with:
-          python-version: '3.11'
+          python-version: '3.14'
       - name: Install dependencies
         run: |
           sudo apt-get install graphviz-dev

.github/workflows/install_and_test.yml

@@ -17,7 +17,7 @@ jobs:
     strategy:
       matrix:
         os: [ ubuntu-latest, macos-latest, windows-latest ]
-        python-version: [ "3.8", "3.9", "3.10", "3.11" ]
+        python-version: [ "3.10", "3.11", "3.12", "3.13", "3.14" ]
 
     steps:
       - uses: actions/checkout@v3

.github/workflows/integration_test.yml

@@ -13,10 +13,10 @@ jobs:
 
     steps:
       - uses: actions/checkout@v3
-      - name: Set up Python 3.11
+      - name: Set up Python 3.14
         uses: actions/setup-python@v4
         with:
-          python-version: 3.11
+          python-version: 3.14
       - name: Installation
         run: |
           python -m pip install --upgrade pip

.github/workflows/prepare_release.yml

@@ -19,7 +19,7 @@ jobs:
       - name: Set up Python
         uses: actions/setup-python@v4
         with:
-          python-version: '3.8'
+          python-version: '3.14'
       - name: Set up dependencies
         run: |
           python -m pip install --upgrade pip