Appsignal V4 Ruby client changes

I came around to update Appsignal gem to the new major version of Appsignal released at the end of August 2024: https://rubygems.org/gems/appsignal/versions/4.0.0

The upgrade was smooth. The real change for my application was to remove the parameter to block to .report_error and use the Appsignal name instead. See for yourself:

There are more changes. In my case, it was the only one needed.