confchange: removed duplicate check in confchange.Simple.

raft/confchange/confchange.go

@@ -142,9 +142,6 @@ func (c Changer) Simple(ccs ...pb.ConfChangeSingle) (tracker.Config, tracker.Pro
 	if n := symdiff(incoming(c.Tracker.Voters), incoming(cfg.Voters)); n > 1 {
 		return tracker.Config{}, nil, errors.New("more than one voter changed without entering joint config")
 	}
-	if err := checkInvariants(cfg, prs); err != nil {
-		return tracker.Config{}, tracker.ProgressMap{}, nil
-	}
 
 	return checkAndReturn(cfg, prs)
 }