chore(deps): Bump docker/build-push-action from 4 to 6

Bumps [docker/build-push-action](https://github.com/docker/build-push-action) from 4 to 6.
- [Release notes](https://github.com/docker/build-push-action/releases)
- [Commits](docker/build-push-action@v4...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

@@ -31,7 +31,7 @@ jobs:
       - name: Save public key to file
         run: 'cp .github/docker/scrt_id_rsa.pub ./scrt_id_rsa.pub'
       - name: Build Git test container
-        uses: docker/build-push-action@v4
+        uses: docker/build-push-action@v6
         with:
           file: .github/docker/Dockerfile_git+openssh
           context: .