Upgrade checkout action

The following actions uses node12 which is deprecated and will be forced to run on node16: actions/checkout@v2. For more info: https://github.blog/changelog/2023-06-13-github-actions-all-actions-will-run-on-node16-instead-of-node12-by-default/

Author: o-liver

.github/workflows/push.yml

@@ -15,7 +15,7 @@ jobs:
       packages: write
       contents: read
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
     - name: Run CI
       run: |
         echo ${{ secrets.DOCKERHUB_PASSWORD }} | docker login -u ${{ secrets.DOCKERHUB_USER }} --password-stdin