Remove redundant sinatra dependency

Author: collabital

platforms-core.gemspec

@@ -27,7 +27,6 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency 'hashie'
   spec.add_development_dependency 'simplecov'
   spec.add_development_dependency 'webmock'
-  spec.add_development_dependency 'sinatra'
   spec.add_development_dependency 'yard'
   spec.add_development_dependency 'yard-activerecord'
 end