Update goquery and add new Single method to `k6/html`

[mstoykov]

https://github.com/PuerkitoBio/goquery/commit/0126a1fd88fe40e3de18dd677e094b46e23d0cb9 added a new method to optimize getting only the first (single) element from a matcher which might be useful for users as well.

[na--]

From what I can see, this update wasn't a breaking change, right? So it's not a blocker for us actually updating the dependency, we can add support for it later, if we decide?