chore(deps): bump docker/build-push-action from 5 to 6 (#382)

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

Author: dependabot[bot]

.github/workflows/build.yml

@@ -87,7 +87,7 @@ jobs:
       - name: Build and publish 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

.github/workflows/pr.yml

@@ -56,7 +56,7 @@ jobs:
           dist/${{ steps.build_variables.outputs.VERSION }}/linux/amd64/spin --version
 
       - name: Build container image
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         with:
           context: .
           file: Dockerfile

.github/workflows/release.yml

@@ -126,7 +126,7 @@ jobs:
       - name: Build and publish 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