switch from http to https for Unicode data file downloads

(patch from MSP-Greg (Greg L), this closes issue #13962)

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@61145 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

tool/downloader.rb

@@ -71,7 +71,7 @@ class Downloader
 
   class Unicode < self
     def self.download(name, *rest)
-      super("http://www.unicode.org/Public/#{name}", name, *rest)
+      super("https://www.unicode.org/Public/#{name}", name, *rest)
     end
   end