Fix filename in comment [ci skip]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@64089 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/irb/completion.rb

@@ -1,6 +1,6 @@
 # frozen_string_literal: false
 #
-#   irb/completor.rb -
+#   irb/completion.rb -
 #   	$Release Version: 0.9$
 #   	$Revision$
 #   	by Keiju ISHITSUKA(keiju@ishitsuka.com)