README: don't need to call to_hash in async anymore

Author: nateberkopec

README.md

@@ -99,9 +99,8 @@ Using a thread to send events will be adequate for truly parallel Ruby platforms
 We recommend creating a background job, using your background job processor, that will send Sentry notifications in the background. Rather than enqueuing an entire Raven::Event object, we recommend providing the Hash representation of an event as a job argument. Here’s an example for ActiveJob:
 
 ```ruby
-config.async = lambda { |event|
-  SentryJob.perform_later(event.to_hash)
-}
+config.async = lambda { |event| SentryJob.perform_later(event) }
+
 class SentryJob < ActiveJob::Base
   queue_as :default