[scroll-animations] Modernize at-scroll-timeline-...-print.html

Bug: 1317765
Change-Id: I30c6e764e30bae1b4b07465d064cbf581f7838b0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3856682


Reviewed-by: Robert Flack <flackr@chromium.org>
Commit-Queue: Anders Hartvoll Ruud <andruud@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1040601}