Correct the check for if we still need to set keys

The prior check had an edge case where once keys were pruned, it'd believe the
keys needed to be set ad infinitum.

coordinator/src/substrate/mod.rs

@@ -243,6 +243,8 @@ async fn handle_block<D: Db, CNT: Clone + Fn(&mut D, TributarySpec), Pro: Proces
       panic!("NewSet event wasn't NewSet: {new_set:?}");
     };
 
+    // If this is Serai, do nothing
+    // We only coordinate/process external networks
     if set.network == NetworkId::Serai {
       continue;
     }