test/ruby/test_iseq.rb: spelling fix: s/diable/disable/

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48880 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* 2014-12-18

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48881 b2dd03c8-39d4-4d8f-98ff-823fe69b080e