ci: bump docker/build-push-action from 5 to 6 (#180)

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-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Mike McDougall <mikemcdougall@gmail.com>

Author: dependabot[bot]

.github/workflows/cite-conformance.yml

@@ -42,7 +42,7 @@ jobs:
             ${{ runner.os }}-buildx-
 
       - name: Build Honua Server image
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         with:
           context: .
           file: ./Dockerfile