io.c: remove unnecessary shared
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@51074 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
io.c: remove unnecessary shared
NUL-terminated and frozen, so it is unnecessary to make it shared.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@51074 b2dd03c8-39d4-4d8f-98ff-823fe69b080e