Clean up tags

[jamsinclair]

A reddit user pointed out unnecessary tags in the data:

I'm curious why most of the cards in N3 are also tagged JLPT_N2 ? It only seems to be the case with this deck. I like what you're doing as I feel like the decks I've been stuck with aren't really maintained. Do you know where we could find example sentences with audio? I suppose that's a big ask.

• https://www.reddit.com/r/LearnJapanese/comments/fvzpd7/open_source_jlpt_anki_decks_help_contribute_and/fmn52ig?utm_source=share&utm_medium=web2x

Let's go through and clean this up.