Actually, don't send _misskey_quote anymore

When we send _misskey_quote, some software (like Fedibird) might incorrectly assume we're Misskey, and try to access other Misskey fields. Turns out it was a bad idea to send this field (obviously, underscored), so we no longer do it.

Now we only send quoteUrl and quoteUri, and stay compatible with Fedibird and Misskey. We continue to ingest all known fields.