Bump webrick from 1.7.0 to 1.9.1 in /docs

Bumps [webrick](https://github.com/ruby/webrick) from 1.7.0 to 1.9.1.
- [Release notes](https://github.com/ruby/webrick/releases)
- [Commits](ruby/webrick@v1.7.0...v1.9.1)

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

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

Author: dependabot[bot]

docs/Gemfile

@@ -6,5 +6,5 @@ gem 'github-pages', group: :jekyll_plugins
 # to publich without github page
 #gem "jekyll"
 
-gem "webrick", "~> 1.7"
+gem "webrick", "~> 1.9"
 gem 'wdm', '>= 0.1.0' if Gem.win_platform?

docs/Gemfile.lock

@@ -272,8 +272,7 @@ GEM
     unf_ext (0.0.8)
     unf_ext (0.0.8-x64-mingw32)
     unicode-display_width (1.8.0)
-    wdm (0.1.1)
-    webrick (1.7.0)
+    webrick (1.9.1)
     zeitwerk (2.4.2)
 
 PLATFORMS
@@ -282,8 +281,7 @@ PLATFORMS
 
 DEPENDENCIES
   github-pages
-  wdm (>= 0.1.0)
-  webrick (~> 1.7)
+  webrick (~> 1.9)
 
 BUNDLED WITH
    2.2.29