build(deps): Bump docker/build-push-action from 5 to 6 (#140)

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>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/build.yml

@@ -84,7 +84,7 @@ jobs:
  uses: docker/setup-buildx-action@v3
 
  - name: Build KDC image
- uses: docker/build-push-action@v5
+ uses: docker/build-push-action@v6
  with:
  context: "{{defaultContext}}:testdata"
  load: true
@@ -94,7 +94,7 @@ jobs:
  cache-to: type=gha,mode=max
 
  - name: Build DNS image
- uses: docker/build-push-action@v5
+ uses: docker/build-push-action@v6
  with:
  context: "{{defaultContext}}:testdata"
  load: true
@@ -104,7 +104,7 @@ jobs:
  cache-to: type=gha,mode=max
 
  - name: Extract keytab
- uses: docker/build-push-action@v5
+ uses: docker/build-push-action@v6
  with:
  context: "{{defaultContext}}:testdata"
  outputs: type=local,dest=testdata