[Fansly] highest quality no longer being downloaded

[koalahntr]

Sometime around April or May, the timeline API stopped providing the highest source quality on new media entities by default. Only the variants contain the highest quality. Sadly, everything that has been syncing for the last several months unfortunately is 720p or so. Most timelines I have checked, it seems to not affect older posts prior to the change, so scraping a fresh timeline today will download source quality for older posts until late April-ish, then switch to 720p.

I'll open a PR as soon as I can fix, but I believe the best approach is to fallback permanently to the existing code that loops through the variants and sorts by height, but the mime types for videos are not consistent either. The top-level media element may be mimetype video/mp4, but the 4k variant may be application/vnd.apple.mpegurl. Will need a new approach to determining the right mimetypes.