Update the max supported Ruby version to 3.1
Update the max supported Ruby version to 3.1

This is actually what's already running because an unquoted '3.0' in the GitHub Actions is truncated to '3', loading the latest Ruby 3 - which at time of writing is Ruby 3.1.1.  This PR makes the change explicit.

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