Update rspec-its requirement from ~> 1.3 to ~> 2.0

Updates the requirements on [rspec-its](https://github.com/rspec/rspec-its) to permit the latest version.
- [Changelog](https://github.com/rspec/rspec-its/blob/main/Changelog.md)
- [Commits](rspec/rspec-its@v1.3.0...v2.0.0)

---
updated-dependencies:
- dependency-name: rspec-its
  dependency-type: direct:development
...

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

govuk_app_config.gemspec

@@ -38,7 +38,7 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency "rails", "~> 7"
   spec.add_development_dependency "rake", "~> 13.0"
   spec.add_development_dependency "rspec", "~> 3.10"
-  spec.add_development_dependency "rspec-its", "~> 1.3"
+  spec.add_development_dependency "rspec-its", "~> 2.0"
   spec.add_development_dependency "rubocop-govuk", "5.0.2"
   spec.add_development_dependency "simplecov"
   spec.add_development_dependency "webmock"