Revert "mute: migrating muted_threads to new mute list"

This reverts commit f341a37902.

damusTests/Mocking/MockDamusState.swift

@@ -44,6 +44,7 @@ func generate_test_damus_state(
                            postbox: .init(pool: pool),
                            bootstrap_relays: .init(),
                            replies: .init(our_pubkey: our_pubkey),
+                           muted_threads: .init(keypair: test_keypair),
                            wallet: .init(settings: settings),
                            nav: .init(),
                            music: .init(onChange: {_ in }),