Move Require shellwords

Move require shellwords to right before calling it because it is not otherwise used in this class.

Author: mzagaja

lib/debug/thread_client.rb

@@ -2,7 +2,6 @@
 
 require 'objspace'
 require 'pp'
-require 'shellwords'
 
 require_relative 'color'
 
@@ -644,6 +643,7 @@ def show_by_editor path = nil
         if editor = (ENV['RUBY_DEBUG_EDITOR'] || ENV['EDITOR'])
           puts "command: #{editor}"
           puts "   path: #{path}"
+          require 'shellwords'
           system(*Shellwords.split(editor), path)
         else
           puts "can not find editor setting: ENV['RUBY_DEBUG_EDITOR'] or ENV['EDITOR']"