Updated the supported Ruby and Rails versions to match current support.
Updated the supported Ruby and Rails versions to match current support.

For Ruby versions:
- Ruby 2.7 is in Security Maintenance
- Ruby 3.0 is in Normal Maintenance
- Ruby 3.1 is in Normal Maintenance

For Rails versions:
- Rails 5.2+ have security support

gocardless/statesman,gocardless/statesman