Bump webrick from 1.7.0 to 1.8.1 in /docs (#630)

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:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

docs/Gemfile.lock

@@ -249,7 +249,7 @@ GEM
       unf_ext
     unf_ext (0.0.8.2)
     unicode-display_width (1.8.0)
-    webrick (1.7.0)
+    webrick (1.8.1)
     zeitwerk (2.6.1)
 
 PLATFORMS