make-snapshot: try downloading Unicode files

Remove empty UNICODE_FILES list to update Unicode files like as
r67025, for 2.6 branch.

[Bug #15593]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@67040 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

tool/make-snapshot

@@ -402,6 +402,7 @@ def package(vcs, rev, destdir, tmp = nil)
       status.scan(/^s([%,])@([A-Za-z_][A-Za-z_0-9]*)@\1(.*?)\1g$/) do
         vars[$2] ||= $3
       end
+      vars.delete("UNICODE_FILES") # for stable branches
       vars["UNICODE_VERSION"] = $unicode_version if $unicode_version
       args = vars.dup
       mk.gsub!(/@([A-Za-z_]\w*)@/) {args.delete($1); vars[$1] || ENV[$1]}