Relax yard pin on 2.7.0

Author: JonRowe

Gemfile

@@ -21,7 +21,11 @@ else
   gem 'rake', '< 11.0.0' # rake 11 requires Ruby 1.9.3 or later
 end
 
-gem 'yard', '~> 0.9.12', :require => false
+if RUBY_VERSION < '2.7.0'
+  gem 'yard', '~> 0.9.12', :require => false
+else
+  gem 'yard'
+end
 
 ### deps for rdoc.info
 group :documentation do