Bump jekyll from 4.1.1 to 4.2.0 in /docs (#3237)

Bumps [jekyll](https://github.com/jekyll/jekyll) from 4.1.1 to 4.2.0.
- [Release notes](https://github.com/jekyll/jekyll/releases)
- [Changelog](https://github.com/jekyll/jekyll/blob/master/History.markdown)
- [Commits](https://github.com/jekyll/jekyll/compare/v4.1.1...v4.2.0)

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

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

docs/Gemfile

@@ -1,7 +1,7 @@
 source 'https://rubygems.org'
 
 group :development, :test do
-  gem 'jekyll', '~> 4.1.1'
+  gem 'jekyll', '~> 4.2.0'
   gem 'jekyll-seo-tag', '~> 2.7.1'
   gem 'jekyll-sitemap', '~> 1.4.0'
   gem 'wdm', '~> 0.1.1', :install_if => Gem.win_platform?