[Sema] Remove dead typedef

rdar://problem/28988750

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@292635 91177308-0d34-0410-b5e6-96231b3b80d8
(cherry picked from commit 14abaea43b00f28bcd9f71381f562dcf05dc0a96)
1 file changed