Update rouge requirement from ~> 4.3.0 to ~> 4.4.0

Updates the requirements on [rouge](https://github.com/rouge-ruby/rouge) to permit the latest version.
- [Release notes](https://github.com/rouge-ruby/rouge/releases)
- [Changelog](https://github.com/rouge-ruby/rouge/blob/master/CHANGELOG.md)
- [Commits](rouge-ruby/rouge@v4.3.0...v4.4.0)

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

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

govuk_design_system_formbuilder.gemspec

@@ -43,7 +43,7 @@ Gem::Specification.new do |s|
   # Required for the guide
   s.add_development_dependency("htmlbeautifier", "~> 1.4.1")
   s.add_development_dependency("nanoc", "~> 4.13.0")
-  s.add_development_dependency("rouge", "~> 4.3.0")
+  s.add_development_dependency("rouge", "~> 4.4.0")
   s.add_development_dependency("rubypants", "~> 0.7.0")
   s.add_development_dependency("sass")
   s.add_development_dependency("sassc", "~> 2.4.0")