Remove duplicate file. (#2496)

deadloop.hlsl already exists with the same content.

tools/clang/test/DXILValidation/deadloop - Copy.hlsl

@@ -1,16 +0,0 @@
-// RUN: %dxc -E main -T ps_6_0 %s  | FileCheck %s
-
-// CHECK: !"llvm.loop.unroll.disable"
-
-int i;
-
-float main(float2 a : A, int3 b : B) : SV_Target
-{
-  float s = 0;
-  
-  while(i < b.x) {
-    s += a.x;
-  }
-
-  return s;
-}