Remove obsolete set call

Summary:
Case case of the switch statement here makes the same call, but it is
already done at the start of the function.

Reviewers: rsmith, dblaikie

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D50409

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@339402 91177308-0d34-0410-b5e6-96231b3b80d8