build(deps-dev): bump @loopback/testlab from 5.0.2 to 6.1.3

Bumps [@loopback/testlab](https://github.com/loopbackio/loopback-next/tree/HEAD/packages/testlab) from 5.0.2 to 6.1.3.
- [Changelog](https://github.com/loopbackio/loopback-next/blob/master/packages/testlab/CHANGELOG.md)
- [Commits](https://github.com/loopbackio/loopback-next/commits/@loopback/testlab@6.1.3/packages/testlab)

---
updated-dependencies:
- dependency-name: "@loopback/testlab"
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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