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 0.135.0 to 0.136.0.
- [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@v0.135.0...v0.136.0)

---
updated-dependencies:
- dependency-name: github.com/open-telemetry/opentelemetry-collector-contrib/testbed
  dependency-version: 0.136.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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Author: dependabot[bot]