Block Party, an anti-harassment service designed to combat abusive content on Twitter, is the latest third-party app to leave the platform in light of Twitter locking most of its API access behind a paywall. Announced in a blog post last night, Block Party’s anti-harassment tools for Twitter are being placed on an immediate, indefinite hiatus, with the developers claiming that changes to Twitter’s API pricing (which starts from $100 per month) have “made it impossible for Block…