chore(deps): update docker/build-push-action action to v6 (#222)

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

.github/workflows/continuous-delivery.yml

@@ -27,7 +27,7 @@ jobs:
           username: ${{ github.repository_owner }}
           password: ${{ secrets.GITHUB_TOKEN }}
       - name: Build and push Nekokai Docker image
-        uses: docker/build-push-action@v5.4.0
+        uses: docker/build-push-action@v6.1.0
         with:
           push: true
           context: .