fix build

Author: Ocmenog

Gemfile

@@ -34,4 +34,4 @@ gem "wdm", "~> 0.1", :platforms => [:mingw, :x64_mingw, :mswin]
 # Lock `http_parser.rb` gem to `v0.6.x` on JRuby builds since newer versions of the gem
 # do not have a Java counterpart.
 gem "http_parser.rb", "~> 0.6.0", :platforms => [:jruby]
-gem "http_proofer", "~> 5.0", :platforms => [:jruby]
+gem "html_proofer", "~> 5.0", :platforms => [:jruby]