Swap notification queue class in before_initialize hook

The initializer approach was running into difficulties in anything other
than a very plain-vanilla rails app. This seems a little better.

instrumentation/rails/lib/opentelemetry/instrumentation/rails/railtie.rb

@@ -11,11 +11,9 @@ module Rails
       # instrumentation, while this Railtie is used to conventionally instrument
       # the Rails application through its initialization hooks.
       class Railtie < ::Rails::Railtie
-        initializer 'opentelemetry.configure_notifications_queue', after: :load_active_support do
+        config.before_initialize do |app|
           ::ActiveSupport::Notifications.notifier = Fanout.new
-        end
 
-        config.before_initialize do |app|
           OpenTelemetry::Instrumentation::ActiveRecord::Instrumentation.instance.install({})
           OpenTelemetry::Instrumentation::Rack::Instrumentation.instance.install({})