On the plus side, if you didn’t opt out before, you get a new opportunity to opt out, which according to the new terms will remove all disputes that have not yet been filed from the scope of previous arbitration agreements with Discord.
Since the clause only applies if you are a US resident, it’s very unclear how that opt-out deadline applies to existing Discord accounts for people who relocate into the US after the deadline. The conservative approach is to opt out wherever in the world you live, in case you later move to the US.