fix: update Python version to 3.9 in workflow files

Author: JakubAndrysek

.github/workflows/publish_pypi.yml

@@ -13,7 +13,7 @@ jobs:
       - name: Set up Python
         uses: actions/setup-python@v5
         with:
-          python-version: "3.7"
+          python-version: "3.9"
       - name: Build packages
         run: bash foreach.sh build
       - name: Publish packages

.github/workflows/test-build-docs.yml

@@ -15,7 +15,7 @@ jobs:
       - name: Set up Python
         uses: actions/setup-python@v5
         with:
-          python-version: "3.7"
+          python-version: "3.9"
       - name: Install dependencies
         run: |
           bash foreach.sh install

.github/workflows/test-build-package.yml

@@ -11,7 +11,7 @@ jobs:
       - name: Set up Python
         uses: actions/setup-python@v5
         with:
-          python-version: "3.7"
+          python-version: "3.9"
       - name: Build packages
         run: |
           bash foreach.sh build

.github/workflows/test-python.yml

@@ -21,7 +21,7 @@ jobs:
     strategy:
       matrix:
         include:
-          - python-version: "3.7"
+          - python-version: "3.9"
             arch: "ARM64"
           - python-version: "3.13"
             arch: "X64"