[AMDGPU][NFC] Remove a redundant test (#146888)

The deleted test is identical to the next test.

Author: paperchalice

llvm/test/CodeGen/AMDGPU/mad-combine.ll

@@ -1,6 +1,5 @@
 ; Make sure we still form mad even when unsafe math or fp-contract is allowed instead of fma.
 
-; RUN: llc -mtriple=amdgcn -mcpu=tahiti -denormal-fp-math-f32=preserve-sign -verify-machineinstrs < %s | FileCheck -enable-var-scope -check-prefix=SI -check-prefix=SI-STD  -check-prefix=SI-STD-SAFE -check-prefix=FUNC %s
 ; RUN: llc -mtriple=amdgcn -mcpu=tahiti -denormal-fp-math-f32=preserve-sign -verify-machineinstrs < %s | FileCheck -enable-var-scope -check-prefix=SI -check-prefix=SI-STD -check-prefix=SI-STD-SAFE -check-prefix=FUNC %s
 ; RUN: llc -mtriple=amdgcn -mcpu=tahiti -denormal-fp-math-f32=preserve-sign -verify-machineinstrs < %s | FileCheck -enable-var-scope -check-prefix=SI -check-prefix=SI-STD -check-prefix=SI-STD-UNSAFE -check-prefix=FUNC %s