Bump webrick from 1.8.1 to 1.8.2 in /docs (#4090)

Bumps [webrick](https://github.com/ruby/webrick) from 1.8.1 to 1.8.2.
- [Release notes](https://github.com/ruby/webrick/releases)
- [Commits](ruby/webrick@v1.8.1...v1.8.2)

---
updated-dependencies:
- dependency-name: webrick
  dependency-type: direct:production
...

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