[coroutines] Mark cxx_status.html of Coroutines TS as (SVN)

Summary: It is time!

Reviewers: GorNishanov, rsmith

Reviewed By: GorNishanov, rsmith

Subscribers: EricWF, rsmith, cfe-commits

Differential Revision: https://reviews.llvm.org/D33624

llvm-svn: 304081