Update readme to use procs

README.md

@@ -135,12 +135,12 @@ For example, we can add hooks in an initializer:
 
 ```ruby
 # Make IP address accessible to the handlers
-Rails.application.config.twirp.service_hooks[:before] = lambda do |rack_env, env|
+Rails.application.config.twirp.service_hooks[:before] = proc do |rack_env, env|
   env[:ip] = rack_env["REMOTE_ADDR"]
 end
 
 # Send exceptions to Honeybadger
-Rails.application.config.twirp.service_hooks[:exception_raised] = ->(exception, _env) { Honeybadger.notify(exception) }
+Rails.application.config.twirp.service_hooks[:exception_raised] = proc {|exception, _env| Honeybadger.notify(exception) }
 ```
 
 ### Middleware