Remove ActiveSupport::Notifications#unsubscribe

[rpbaltazar]

Copied from the Original PR

Hi Rails-on-Services! 👋

I'm a developer on the New Relic Ruby Agent team. I recently discovered that the config.active_record_log option disables all Datastore recording for our newrelic_rpm gem.

The culprit seems to be the line removed in this PR. Calling #unsubscribe on ActiveSupport::Notifications interferes with the strategy many gems use to instrument ActiveRecord's behavior.

My intention behind this PR is to start a conversation about why the #unsubscribe method is called and if we can find another way achieve its goal.

Thanks for your time and for picking up the torch on this great library. 🔥