lib/rubygems: bump up RubyGems version to 2.6.12. [Backport #13842]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_4@59813 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
lib/rubygems: bump up RubyGems version to 2.6.12. [Backport #13842]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_4@59813 b2dd03c8-39d4-4d8f-98ff-823fe69b080e