Change the Pixiv artist profile URL to the new format for artist creations

[BrokenEagle]

See forum #16887. Basically, we should start using the new format, with the preferred one being the default. Many other users that are fixing up artist entries are already doing this, but there are still many that are still being created and left with the old format.

This won't be a mass-update of all artist entries at once to the new format, it'll just be changing the URLs provided to the user when clicking the "Create artist" button on the post page.