html5lib/runner.html is too slow and needs to be split into multiple tests
It's too slow as of bug 110643.
See also https://bugs.webkit.org/show_bug.cgi?id=110734 for other slow html5lib tests
This should just be solved by moving to the up-to-date copy of the html5lib tests in web-platform-tests (/html/syntax/parsing/html5lib_*). That both will keep it up-to-date and makes it run some of the newer formats correctly (#script-on, #script-off, content for template subtrees, etc.).