[ruby/net-protocol] Bump version to 0.2.1

https://github.com/ruby/net-protocol/commit/06d1420936

lib/net/protocol.rb

@@ -26,7 +26,7 @@ require 'io/wait'
 module Net # :nodoc:
 
   class Protocol   #:nodoc: internal use only
-    VERSION = "0.2.0"
+    VERSION = "0.2.1"
 
     private
     def Protocol.protocol_param(name, val)