build(deps): 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](https://github.com/docker/build-push-action/compare/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/ci.yml

@@ -108,7 +108,7 @@ jobs:
           buildkitd-flags: --debug
       -
         name: Build
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         with:
           context: .
           platforms: linux/amd64,linux/arm64,linux/ppc64le
@@ -254,7 +254,7 @@ jobs:
           buildkitd-config: /tmp/buildkitd.toml
       -
         name: Build
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         with:
           context: .
 
@@ -281,7 +281,7 @@ jobs:
               mirrors = ["mirror.gcr.io"]
       -
         name: Build
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         with:
           context: .