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/ci.yml

@@ -120,7 +120,7 @@ jobs:
             type=ref,event=tag,enable=true,priority=600
             type=ref,event=pr,prefix=pr-,enable=true,priority=600
       - name: Build and push to local (test) registry
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         with:
           context: .
           file: ./Dockerfile
@@ -158,7 +158,7 @@ jobs:
             type=ref,event=pr,prefix=pr-,enable=true,priority=600
       - name: Build and push to public registry(s)
         if: ${{ fromJSON(env.PUSH) }}
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         with:
           context: .
           file: ./Dockerfile