vm.inc.tmpl + instruction.rb: typo fixes

* template/vm.inc.tmpl: "insns.c" => "insns.def"
* tool/instruction.rb: typo fix

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47585 b2dd03c8-39d4-4d8f-98ff-823fe69b080e