Update rspec requirement from ~> 3.4.0 to ~> 3.13.0

Updates the requirements on [rspec](https://github.com/rspec/rspec-metagem) to permit the latest version.
- [Commits](rspec/rspec-metagem@v3.4.0...v3.13.0)

---
updated-dependencies:
- dependency-name: rspec
  dependency-type: direct:production
...

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

Author: dependabot[bot]

rspec_api_documentation.gemspec

@@ -36,7 +36,7 @@ Gem::Specification.new do |s|
   s.add_development_dependency "contracts", "~> 0.13.0"
   s.add_development_dependency "gherkin", "~> 3.2.0"
   s.add_development_dependency "multi_json", "~> 1.11.2"
-  s.add_development_dependency "rspec", "~> 3.4.0"
+  s.add_development_dependency "rspec", "~> 3.0"
 
   s.files        = Dir.glob("lib/**/*") + Dir.glob("templates/**/*")
   s.require_path = "lib"