build(deps): 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] <[email protected]>

.github/workflows/deployment.yml

@@ -45,7 +45,7 @@ jobs:
           password: ${{ secrets.GITHUB_TOKEN }}
 
       - name: Build Docker image (dev)
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         with:
           context: .
           push: ${{ github.event_name == 'push' && github.repository == 'DIRACGrid/diracx-web' && github.ref_name == 'main' }}
@@ -72,7 +72,7 @@ jobs:
 
       - name: Build Docker image
         if: ${{ needs.release-please.outputs.release_created == 'true' }}
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         with:
           context: .
           push: true