Roto (Kanae)

BUR #6387 has been approved by @evazion.

rename roto_(nijisanji) -> roto_(kanae)

Two tags for the same character, using Kanae as the qualifier since that's the standard for vtuber mascots/pets (see Pikl (Elira Pendora), Bibi (Tokoyami Towa), etc.)

While I don't disagree with this, there are plenty of Kanaes on Danbooru, so the qualifier ends up looking a tad ambiguous (which is probably why Nijisanji is the more populous qualifier). Maybe roto (kanae) (nijisanji)'d be better?

The bulk update request #6387 (forum #192237) has been approved by @evazion.