Update generator_spec requirement from ~> 0.9.3 to ~> 0.10.0

Updates the requirements on [generator_spec](https://github.com/stevehodgkiss/generator_spec) to permit the latest version.
- [Commits](stevehodgkiss/generator_spec@0.9.3...v0.10.0)

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

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

doorkeeper.gemspec

@@ -50,7 +50,7 @@ Gem::Specification.new do |gem|
   gem.add_development_dependency "coveralls_reborn"
   gem.add_development_dependency "database_cleaner", "~> 2.0"
   gem.add_development_dependency "factory_bot", "~> 6.0"
-  gem.add_development_dependency "generator_spec", "~> 0.9.3"
+  gem.add_development_dependency "generator_spec", "~> 0.10.0"
   gem.add_development_dependency "grape"
   gem.add_development_dependency "rake", ">= 11.3.0"
   gem.add_development_dependency "rspec-rails"