fix rebase of new mutation guide
fix rebase of new mutation guide

rmosolgo/graphql-ruby,rmosolgo/graphql-ruby,nevesenin/graphql-ruby,rmosolgo/graphql-ruby,nevesenin/graphql-ruby,nevesenin/graphql-ruby,nevesenin/graphql-ruby,rmosolgo/graphql-ruby,xuorig/graphql-ruby,xuorig/graphql-ruby,xuorig/graphql-ruby