Function docs: update types usage
Function docs: update types usage

`types` is exposed in functions as of `1.5.6`

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