Fix container query WPT tests to reflect recent WG resolution.
As per CSSWG resolution in:
w3c/csswg-drafts#5984 (comment)
Differential Revision: https://phabricator.services.mozilla.com/D212412
bugzilla-url: https://bugzilla.mozilla.org/show_bug.cgi?id=1790886
gecko-commit: bc97304e5b3d4d2110fd8f2120ba9914406a116a
gecko-reviewers: jwatt