Drop redefined accessor methods (#353)

Author: danhalligan

lib/slack/real_time/client.rb

@@ -20,7 +20,6 @@ class << self
       attr_accessor :store
       attr_accessor :url
       attr_accessor(*Config::ATTRIBUTES)
-      attr_accessor :logger
 
       protected :store_class, :store_class=
 

lib/slack/real_time/config.rb

@@ -17,7 +17,8 @@ class NoConcurrencyError < StandardError; end
         logger
       ].freeze
 
-      attr_accessor(*Config::ATTRIBUTES)
+      attr_accessor(*Config::ATTRIBUTES - [:concurrency])
+      attr_writer :concurrency
 
       def reset
         self.websocket_ping = 30