AMDGPU: Remove a FileCheck from an XFAILed test

In case the assert ever stops, we don't want to hit the FileCheck error
from there being no checks.

Author: arsenm

llvm/test/CodeGen/AMDGPU/infinite-loop-evergreen.ll

@@ -1,6 +1,6 @@
 ; XFAIL: *
 ; REQUIRES: asserts
-; RUN: llc -mtriple=r600 -mcpu=cypress < %s | FileCheck %s
+; RUN: llc -mtriple=r600 -mcpu=cypress < %s
 
 define amdgpu_kernel void @inf_loop_irreducible_cfg() nounwind {
 entry: