Fix deprecation warning in Rails 7.1

[jamie]

I recently upgraded my Rails app to 7.1, and am getting a lot of the following in my logs:

DEPRECATION WARNING: Calling `ActiveRecord::Base.clear_active_connections! is deprecated. Please call the method directly on the connection handler; for example: `ActiveRecord::Base.connection_handler.clear_active_connections!`. (called from clear_active_connections! at /Users/jamie/code/realworld-rails-hotwire/vendor/bundle/ruby/3.2.0/gems/activerecord-7.1.1/lib/active_record/connection_handling.rb:323)

Adding some extra debugging in active_record/connection_handling.rb pointed at lib/scout_apm/app_server_load.rb:54 being the actual callsite in question.

I'm not sure how backward compatible this change is (or how old of Rails is supported by Scout) but this change does clear the deprecation.

[jrothrock]

Thanks for the PR!

We support backdown to Rails 2.2 currently... which it looks like this is compatible with!