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/docker-pi-hole-base.yml

@@ -63,7 +63,7 @@ jobs:
           password: ${{ secrets.GITHUB_TOKEN }}
       -
         name: Build and push
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         with:
           context: docker-pi-hole-base/.
           platforms: ${{ matrix.job.PLATFORMS }}

.github/workflows/ftl-build.yml

@@ -77,7 +77,7 @@ jobs:
         uses: docker/setup-buildx-action@v3
       -
         name: Build container and test-compile FTL
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         with:
           context: ftl-build
           platforms: ${{ matrix.platform }}
@@ -91,7 +91,7 @@ jobs:
         name: Push builder target and push by digest
         if: github.event_name != 'pull_request'
         id: build_docker
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         with:
           context: ftl-build
           platforms: ${{ matrix.platform }}