Typo in a gvar name

* ext/tk/sample/demos-jp/hscale.rb: $hscale_deom => $hscale_demo

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@53335 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ext/tk/sample/demos-jp/hscale.rb

@@ -2,7 +2,7 @@
 # frozen_string_literal: false
 require "tkcanvas"
 
-if defined?($hscale_demo) && $hscale_deom
+if defined?($hscale_demo) && $hscale_demo
   $hscale_demo.destroy
   $hscale_demo = nil
 end