Remove loading Puppet version

Previous versions of the Rakefile relied on Puppet#version as part of a
packaging task. That packaging task was removed from the Rakefile in
2012 in b1648b2, so we no longer need to load the Puppet library and
require puppet/version.

Author: mhashizume

Rakefile

@@ -1,9 +1,5 @@
 # frozen_string_literal: true
 
-# We need access to the Puppet.version method
-$LOAD_PATH.unshift(File.expand_path("lib"))
-require 'puppet/version'
-
 require 'open3'
 require 'rake'
 require 'rubygems'