Remove Serai from the ConfirmDkgTask

coordinator/substrate/src/publish_slash_report.rs

@@ -31,6 +31,8 @@ impl<D: Db> PublishSlashReportTask<D> {
       return Ok(false);
     };
 
+    // This uses the latest finalized block, not the latest cosigned block, which should be
+    // fine as in the worst case, the only impact is no longer attempting TX publication
     let serai = self.serai.as_of_latest_finalized_block().await.map_err(|e| format!("{e:?}"))?;
     let serai = serai.validator_sets();
     let session_after_slash_report = Session(session.0 + 1);