`.on_success` should return the block result not the instance

[arturictus]

out = GithubCLI::User.new(username: 'arturictus')
               .on_success do |inst|
                 inst.status_code # => 200
                 inst.body # => {"login"=>"arturictus", "id"=>1930175, ...}
                 # do something useful
               end.on_error do |inst|
                 puts "Error retrieving use"
               end

Right now out is the User instance. Should be the body