Bump webrick from 1.7.0 to 1.8.1

Bumps [webrick](https://github.com/ruby/webrick) from 1.7.0 to 1.8.1.
- [Release notes](https://github.com/ruby/webrick/releases)
- [Commits](ruby/webrick@v1.7.0...v1.8.1)

---
updated-dependencies:
- dependency-name: webrick
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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