4bc8fab4f5 added support for `proxy: false` on attachment URLs in
translators, but it made that flag skip `resolveURL()` altogether, which
meant that relative URLs weren't resolved, rather than just skipping
proxying.
This may fix PDF downloads for some ScienceDirect pages (though I can't
test this one):
https://forums.zotero.org/discussion/85884/problem-downloading-pdf-via-zotero
9fdf82aca5