Update actions/checkout action to v6 (#277)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/build-backend.yml

@@ -21,7 +21,7 @@ jobs:
       SHOULD_PUSH: ${{ github.event_name != 'pull_request' && github.ref == 'refs/heads/master' && secrets.DOCKER_REGISTRY_USERNAME != '' }}
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
       - name: Docker meta
         id: meta
         uses: docker/metadata-action@v5

.github/workflows/build-frontend.yml

@@ -22,7 +22,7 @@ jobs:
       DEPLOYMENT_WEBHOOK_URL: ${{ secrets.DEPLOYMENT_WEBHOOK_URL }}
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
       - name: Docker meta
         id: meta
         uses: docker/metadata-action@v5