Update sinatra requirement from ~> 1.4.7 to ~> 2.0.8

Updates the requirements on [sinatra](https://github.com/sinatra/sinatra) to permit the latest version.
- [Changelog](https://github.com/sinatra/sinatra/blob/main/CHANGELOG.md)
- [Commits](sinatra/sinatra@v1.4.7...v2.0.8.1)

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

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

rspec_api_documentation.gemspec

@@ -20,7 +20,7 @@ Gem::Specification.new do |s|
 
   s.add_development_dependency "bundler", ">= 1.16"
   s.add_development_dependency "fakefs", "~> 0.6.0"
-  s.add_development_dependency "sinatra", "~> 1.4.7"
+  s.add_development_dependency "sinatra", "~> 2.0.8"
   s.add_development_dependency "aruba", "~> 0.14.14"
   s.add_development_dependency "capybara", "~> 3.39.2"
   s.add_development_dependency "rake", "~> 10.5.0"