updates python version to be explicit, updates actions/checkout

Author: sphawes

.github/workflows/ci.yaml

@@ -9,10 +9,10 @@ jobs:
   deploy:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/setup-python@v4
         with:
-          python-version: 3.x
+          python-version: 3.12
       - run: pip install -r requirements.txt
       - run: sudo apt-get update
       - run: sudo apt-get install imagemagick pngquant