Fix CI for MacOS

Author: valeros

.github/workflows/examples.yml

@@ -7,7 +7,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [ubuntu-latest, windows-latest, macos-latest]
+        os: [ubuntu-latest, windows-latest, macos-13]
         example:
           - "examples/arduino-blink"
           - "examples/arduino-ble-led"
@@ -29,7 +29,7 @@ jobs:
       - name: Set up Python 3
         uses: actions/setup-python@v3
         with:
-          python-version: "3.7"
+          python-version: "3.9"
       - name: Install dependencies
         run: |
           pip install -U https://github.com/platformio/platformio/archive/develop.zip