Fixed running script elements with a type attribute value with whitespace
(like " ").

Fixed by comparing value emptiness before and after trim, if not empty
before and empty after, undo the trim.

2 WPT subtests now newly pass.

WPT tests: https://wpt.fyi/results/html/semantics/scripting-1/the-script-element/script-type-and-language-js.html

Differential Revision: https://phabricator.services.mozilla.com/D178573