benchmark.javascript: update jquery to 3.5.1 to avoid noisy XSS warnings.

benchmark.javascript: update jquery to 3.5.1 to avoid noisy XSS warnings.

See #2403:

> Versions of jQuery (prior to 3.5) have a fairly recent XSS
> vulnerability:
> https://www.infoq.com/news/2020/04/jquery-35-xss-vulnerability-fix/

> It looks like the file is not used in any way that would expose the
> XSS bug, but for what it's worth it gets flagged as sketchy by some
> kinds of vulnerability scans my current project uses. Maybe other users
> will get that noise too?