build(deps): bump docker/build-push-action from 6.13.0 to 6.15.0

Bumps [docker/build-push-action](https://github.com/docker/build-push-action) from 6.13.0 to 6.15.0.
- [Release notes](https://github.com/docker/build-push-action/releases)
- [Commits](https://github.com/docker/build-push-action/compare/ca877d9245402d1537745e0e356eab47c3520991...471d1dc4e07e5cdedd4c2171150001c434f0b7a4

)

---
updated-dependencies:
- dependency-name: docker/build-push-action
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>