Update webrick requirement from ~> 1.8.0 to ~> 1.9.0

Updates the requirements on [webrick](https://github.com/ruby/webrick) to permit the latest version.
- [Release notes](https://github.com/ruby/webrick/releases)
- [Commits](ruby/webrick@v1.8.0...v1.9.0)

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

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

vagrant-parallels.gemspec

@@ -23,7 +23,7 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency 'rake', '~> 13.0'
   spec.add_development_dependency 'rspec', '~> 3.11'
   spec.add_development_dependency 'rspec-its', '~> 2.0.0'
-  spec.add_development_dependency 'webrick', '~> 1.8.0'
+  spec.add_development_dependency 'webrick', '~> 1.9.0'
 
   spec.files = Dir['lib/**/*', 'locales/**/*', 'README.md', 'CHANGELOG.md', 'LICENSE.txt']
   spec.require_path = 'lib'