AMDGPU/SI: Remove unnecessary run lines from test

Summary:
This test had run lines disabling/enabling the promote alloca pass, but
enabling/disabling promote alloca had no impact on the output.

Reviewers: arsenm

Subscribers: mgrang, kzhuravl, wdng, nhaehnle, yaxunl, llvm-commits, tony-tye

Differential Revision: https://reviews.llvm.org/D25787

llvm-svn: 285197