[ruby/timeout] timeout.rb: Update documentation

This is a followup to #49.

https://github.com/ruby/timeout/commit/683fdb45ee

lib/timeout.rb

@@ -4,7 +4,7 @@
 # == Synopsis
 #
 #   require 'timeout'
-#   status = Timeout::timeout(5) {
+#   status = Timeout.timeout(5) {
 #     # Something that should be interrupted if it takes more than 5 seconds...
 #   }
 #
@@ -13,10 +13,6 @@
 # Timeout provides a way to auto-terminate a potentially long-running
 # operation if it hasn't finished in a fixed amount of time.
 #
-# Previous versions didn't use a module for namespacing, however
-# #timeout is provided for backwards compatibility.  You
-# should prefer Timeout.timeout instead.
-#
 # == Copyright
 #
 # Copyright:: (C) 2000  Network Applied Communication Laboratory, Inc.