Bump github.com/open-telemetry/opentelemetry-collector-contrib/testbed

Bumps [github.com/open-telemetry/opentelemetry-collector-contrib/testbed](https://github.com/open-telemetry/opentelemetry-collector-contrib) from 0.85.0 to 0.87.0.
- [Release notes](https://github.com/open-telemetry/opentelemetry-collector-contrib/releases)
- [Changelog](https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/main/CHANGELOG-API.md)
- [Commits](open-telemetry/opentelemetry-collector-contrib@v0.85.0...v0.87.0)

---
updated-dependencies:
- dependency-name: github.com/open-telemetry/opentelemetry-collector-contrib/testbed
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>