update sanitize

Author: kenyonj

github-markup.gemspec

@@ -23,7 +23,7 @@ Gem::Specification.new do |s|
   s.add_development_dependency "activesupport", "~> 4.0"
   s.add_development_dependency "minitest", "~> 5.4", ">= 5.4.3"
   s.add_development_dependency "html-pipeline", "~> 1.0"
-  s.add_development_dependency "sanitize", ">= 4.6.3"
+  s.add_development_dependency "sanitize", "~> 6.1.0"
   s.add_development_dependency "nokogiri", "~> 1.16.5"
   s.add_development_dependency "nokogiri-diff", "~> 0.3.0"
   s.add_development_dependency "github-linguist", "~> 7.30.0"