[WebGPU] stencilAttachmentPixelFormat is never set on the MTLDepthStencilDescriptor
<rdar://problem/117213772>
Pull request: https://github.com/WebKit/WebKit/pull/19285
Committed 269556@main (ac19d2a124a3): <https://commits.webkit.org/269556@main> Reviewed commits have been landed. Closing PR #19285 and removing active labels.