Bump webrick from 1.7.0 to 1.8.2 in /docs

Bumps [webrick](https://github.com/ruby/webrick) from 1.7.0 to 1.8.2.
- [Release notes](https://github.com/ruby/webrick/releases)
- [Commits](ruby/webrick@v1.7.0...v1.8.2)

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

Signed-off-by: dependabot[bot] <support@github.com>

docs/Gemfile.lock

@@ -281,7 +281,7 @@ GEM
       unf_ext
     unf_ext (0.0.8.1)
     unicode-display_width (1.8.0)
-    webrick (1.7.0)
+    webrick (1.8.2)
 
 PLATFORMS
   ruby