Bump underscore from 1.6.0 to 1.13.8

Bumps [underscore](https://github.com/jashkenas/underscore) from 1.6.0 to 1.13.8.
- [Commits](https://github.com/jashkenas/underscore/commits)

---
updated-dependencies:
- dependency-name: underscore
  dependency-version: 1.13.8
  dependency-type: indirect
...

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Author: dependabot[bot]