test(cts): add failing entry for webgpu:api,operation,buffers,map:mapAsync,read:*

Author: ErichDonGubler

cts_runner/test.lst

@@ -4,6 +4,7 @@
 // ```
 unittests:*
 webgpu:api,operation,buffers,createBindGroup:buffer_binding_resource:*
+fails-if(vulkan,dx12,metal): webgpu:api,operation,buffers,map:mapAsync,read:*
 webgpu:api,operation,command_buffer,basic:*
 webgpu:api,operation,command_buffer,copyBufferToBuffer:*
 fails-if(vulkan) webgpu:api,operation,command_buffer,copyTextureToTexture:copy_depth_stencil:format="depth24plus"