[Vulkan] Change non-uniform index test to succeed for Clang && Vulkan. (#468)

Verified the test is succeeding from the the fix in
llvm/llvm-project#162540

Author: luciechoi

test/Feature/ResourceArrays/unbounded-array-nuri.test

@@ -64,7 +64,7 @@ DescriptorSets:
 #--- end
 
 # Bug https://github.com/llvm/llvm-project/issues/159679
-# XFAIL: Clang
+# XFAIL: Clang && DirectX
 
 # Resource arrays are not yet supported on Metal
 # UNSUPPORTED: Metal