chore(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](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/build.yml

@@ -49,7 +49,7 @@ jobs:
       - name: Build and publish slim container image
         # Only run this on repositories in the 'spinnaker' org, not on forks.
         if: startsWith(github.repository, 'spinnaker/')
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         with:
           context: .
           file: Dockerfile.slim
@@ -63,7 +63,7 @@ jobs:
       - name: Build and publish ubuntu container image
         # Only run this on repositories in the 'spinnaker' org, not on forks.
         if: startsWith(github.repository, 'spinnaker/')
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         with:
           context: .
           file: Dockerfile.ubuntu

.github/workflows/pr.yml

@@ -32,7 +32,7 @@ jobs:
           ORG_GRADLE_PROJECT_version: ${{ steps.build_variables.outputs.VERSION }}
         run: ./gradlew build ${{ steps.build_variables.outputs.REPO }}-web:installDist
       - name: Build slim container image
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         with:
           context: .
           file: Dockerfile.slim
@@ -43,7 +43,7 @@ jobs:
             "${{ env.CONTAINER_REGISTRY }}/${{ steps.build_variables.outputs.REPO }}:latest-slim"
             "${{ env.CONTAINER_REGISTRY }}/${{ steps.build_variables.outputs.REPO }}:${{ steps.build_variables.outputs.VERSION }}-slim"
       - name: Build ubuntu container image
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         with:
           context: .
           file: Dockerfile.ubuntu

.github/workflows/release.yml

@@ -70,7 +70,7 @@ jobs:
       - name: Build and publish slim container image
         # Only run this on repositories in the 'spinnaker' org, not on forks.
         if: startsWith(github.repository, 'spinnaker/')
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         with:
           context: .
           file: Dockerfile.slim
@@ -83,7 +83,7 @@ jobs:
       - name: Build and publish ubuntu container image
         # Only run this on repositories in the 'spinnaker' org, not on forks.
         if: startsWith(github.repository, 'spinnaker/')
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         with:
           context: .
           file: Dockerfile.ubuntu