When getting the computed style of a grid item that has a trimmed margin, it should be reported as 0
<rdar://problem/106559103>
Pull request: https://github.com/WebKit/WebKit/pull/12483
Committed 262967@main (c87ee9281557): <https://commits.webkit.org/262967@main> Reviewed commits have been landed. Closing PR #12483 and removing active labels.
Submitted web-platform-tests pull request: https://github.com/web-platform-tests/wpt/pull/39602