Bump docker/build-push-action from 5 to 6

Bumps [docker/build-push-action](https://github.com/docker/build-push-action) from 5 to 6.
- [Release notes](https://github.com/docker/build-push-action/releases)
- [Commits](docker/build-push-action@v5...v6)

---
updated-dependencies:
- dependency-name: docker/build-push-action
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/ci.yml

@@ -49,7 +49,7 @@ jobs:
     - name: 🧰 Set up Docker Buildx
       uses: docker/setup-buildx-action@v3
     - name: 🚀 Build image
-      uses: docker/build-push-action@v5
+      uses: docker/build-push-action@v6
       with:
         context: .
         push: false
@@ -270,7 +270,7 @@ jobs:
           webis/ir_axioms
           ghcr.io/${{ github.repository }}
     - name: 🚀 Build and push image
-      uses: docker/build-push-action@v5
+      uses: docker/build-push-action@v6
       with:
         context: .
         push: true