probes_helper.h (RUBY_DTRACE_HOOK): correct type for _id

* probes_helper.h (RUBY_DTRACE_HOOK): correct type for _id
  I want to experiment with uint32_t ID

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@44966 b2dd03c8-39d4-4d8f-98ff-823fe69b080e