date_core.c: fix DateTime rdoc
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@54444 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
date_core.c: fix DateTime rdoc
of DateTime. [ruby-core:74729] [Bug #12233]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@54444 b2dd03c8-39d4-4d8f-98ff-823fe69b080e