Update rake requirement from ~> 10.0 to ~> 13.1 (#23)

Updates the requirements on [rake](https://github.com/ruby/rake) to permit the latest version.
- [Release notes](https://github.com/ruby/rake/releases)
- [Changelog](https://github.com/ruby/rake/blob/master/History.rdoc)
- [Commits](ruby/rake@rake-10.0.0...v13.1.0)

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

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

sinject.gemspec

@@ -28,7 +28,7 @@ Gem::Specification.new do |spec|
   spec.require_paths = ['lib']
 
   spec.add_development_dependency 'bundler', '>= 1.11'
-  spec.add_development_dependency 'rake', '~> 10.0'
+  spec.add_development_dependency 'rake', '~> 13.1'
   spec.add_development_dependency 'rspec', '~> 3.0'
   spec.add_development_dependency 'simplecov'
   spec.add_development_dependency 'simplecov_json_formatter'