The setup checklist that could never be finished is gone

There is nothing to do. The old checklist no longer opens over your first post, and the sidebar and badge that came with it are gone. Your first run still walks you from your voice to your first written post, so nothing you relied on is missing. One of the old steps had been impossible to complete since March, which meant the list sat there unfinished for everyone who saw it. Any points you already earned from it are untouched and still count towards your leaderboard position.