Revert "Fix encoding issue deserializing responses"

This reverts commit c987c91.

Author: dlau

lib/ldclient-rb/requestor.rb

@@ -9,7 +9,7 @@ def initialize(sdk_key, config)
       @sdk_key = sdk_key
       @config = config
       @client = Faraday.new do |builder|
-        builder.use :http_cache, store: @config.cache_store, serializer: Marshal
+        builder.use :http_cache, store: @config.cache_store
 
         builder.adapter :net_http_persistent
       end