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] <[email protected]>

.github/workflows/build.yml

@@ -65,7 +65,7 @@ jobs:
             type=ref,event=tag
             type=ref,event=pr,prefix=pr-
       - name: Build and push (debian)
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         with:
           push: ${{ !(env.ACT || github.actor == 'dependabot[bot]') }}
           context: .
@@ -74,7 +74,7 @@ jobs:
           tags: ${{ steps.meta_debian.outputs.tags }}
           labels: ${{ steps.meta_debian.outputs.labels }}
       - name: Build and push (scratch)
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         with:
           push: ${{ !(env.ACT || github.actor == 'dependabot[bot]') }}
           context: .