test_rational.rb: fix default external
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@51830 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
test_rational.rb: fix default external
encoding, which affects inspect results.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@51830 b2dd03c8-39d4-4d8f-98ff-823fe69b080e