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/release.yml

@@ -36,7 +36,7 @@ jobs:
           images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}/geotrek-rando-builder
 
       - name: Build and push Docker image
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         with:
           context: frontend
           file: ./frontend/Dockerfile
@@ -45,7 +45,7 @@ jobs:
           labels: ${{ steps.meta.outputs.labels }}
 
       - name: Build and push Docker image builder
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         with:
           context: frontend
           file: ./frontend/Dockerfile