[spirv] Use sm 6.5 as 6.6 is not fully supported yet. (#3191)

tools/clang/test/CodeGenSPIRV/vk.1p2.remove.bufferblock.runtimearray.hlsl

@@ -1,4 +1,4 @@
-// Run: %dxc -T cs_6_6 -E main -fspv-target-env=vulkan1.2
+// Run: %dxc -T cs_6_5 -E main -fspv-target-env=vulkan1.2
 
 struct MeshPart {
   uint indexOffset;