build(deps): bump github.com/prometheus/exporter-toolkit

Bumps [github.com/prometheus/exporter-toolkit](https://github.com/prometheus/exporter-toolkit) from 0.13.0 to 0.13.1.
- [Release notes](https://github.com/prometheus/exporter-toolkit/releases)
- [Changelog](https://github.com/prometheus/exporter-toolkit/blob/master/CHANGELOG.md)
- [Commits](https://github.com/prometheus/exporter-toolkit/compare/v0.13.0...v0.13.1

)

---
updated-dependencies:
- dependency-name: github.com/prometheus/exporter-toolkit
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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