Auto merge of #26042 - jdm:webxrup, r=Manishearth
Auto merge of #26042 - jdm:webxrup, r=Manishearth

Update webxr and webxr-api.

This allows us to re-enter immersive mode on HoloLens, and also allows us to test immersive-ar scenes in the glwindow backend.

splav/servo,splav/servo,splav/servo,splav/servo,KiChjang/servo,splav/servo,KiChjang/servo,KiChjang/servo,splav/servo,KiChjang/servo,KiChjang/servo,KiChjang/servo,splav/servo,KiChjang/servo,splav/servo,KiChjang/servo,splav/servo,KiChjang/servo,KiChjang/servo,splav/servo