Bump webrick from 1.8.2 to 1.9.1

Bumps [webrick](https://github.com/ruby/webrick) from 1.8.2 to 1.9.1.
- [Release notes](https://github.com/ruby/webrick/releases)
- [Commits](ruby/webrick@v1.8.2...v1.9.1)

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

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

Gemfile

@@ -25,7 +25,7 @@ end
 # Excluded from CI except on latest MRI Ruby, to reduce compatibility burden
 group :docs, optional: true do
   gem "redcarpet", "~> 3.6"
-  gem "webrick", "~> 1.8"
+  gem "webrick", "~> 1.9"
   gem "yard", "~> 0.9"
   gem "yard-doctest", "~> 0.1"
 end

Gemfile.lock

@@ -82,7 +82,7 @@ GEM
     slop (3.6.0)
     unicode-display_width (2.5.0)
     values (1.8.0)
-    webrick (1.8.2)
+    webrick (1.9.1)
     yard (0.9.36)
     yard-doctest (0.1.17)
       minitest
@@ -101,7 +101,7 @@ DEPENDENCIES
   simplecov
   simplecov-cobertura
   values (~> 1)
-  webrick (~> 1.8)
+  webrick (~> 1.9)
   yard (~> 0.9)
   yard-doctest (~> 0.1)