[css-nesting] Don't emit invisible rules inside @page

The parsing code for @page leans on the code from CSS Nesting, which recently gained special behavior for trailing declarations (crbug.com/1517290). This special behavior affects how an inner rule relates to its outer style rule (/selector), which is not relevant for @page.

Bug: 1517290 Change-Id: I755f8b2675f8e5c988c8ea5afdf03c84b779da83 Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5272554 Commit-Queue: Morten Stenshorne mstensho@chromium.org Commit-Queue: Anders Hartvoll Ruud andruud@chromium.org Reviewed-by: Morten Stenshorne mstensho@chromium.org Cr-Commit-Position: refs/heads/main@{#1258458}