Mark view-timeline-pseudo-on-scroller.html as tentative

### Test List

https://wpt.fyi/results/scroll-animations/css/view-timeline-pseudo-on-scroller.html

### Rationale

I believe that this test should be marked as tentative pending clarification in the spec on how view-timelines should work with inline or fragmented subjects.

See https://github.com/w3c/csswg-drafts/issues/13818







