Disable the test on Metal

Issue #6029 is filed for fixing the Metal case.

Author: aleino-nv

tests/expected-failure-github.txt

@@ -8,6 +8,7 @@ tests/render/render0.hlsl (mtl)
 tests/render/multiple-stage-io-locations.slang (mtl)
 tests/render/nointerpolation.hlsl (mtl)
 tests/serialization/obfuscated-serialized-module-test.slang.2 syn (mtl)
+tests/wgsl/bitshifts.slang syn (mtl)
 tests/autodiff/custom-intrinsic.slang.2 syn (wgpu)
 tests/bugs/buffer-swizzle-store.slang.3 syn (wgpu)
 tests/compute/interface-shader-param-in-struct.slang.4 syn (wgpu)

tests/wgsl/bitshifts.slang

@@ -1,4 +1,6 @@
 //TEST(compute):COMPARE_COMPUTE:-shaderobj
+// Issue #6029: Generates invalid Metal code
+//DISABLE_TEST(compute):COMPUTE_COMPARE:-mtl
 
 //TEST_INPUT:ubuffer(data=[3 7 8 10], stride=4):name=inputBuffer
 RWStructuredBuffer<int> inputBuffer;