v3rpc: set canceled=true when stream is compacted

Fixes #8231

etcdserver/api/v3rpc/watch.go

@@ -321,11 +321,13 @@ func (sws *serverWatchStream) sendLoop() {
 				}
 			}
 
+			canceled := wresp.CompactRevision != 0
 			wr := &pb.WatchResponse{
 				Header:          sws.newResponseHeader(wresp.Revision),
 				WatchId:         int64(wresp.WatchID),
 				Events:          events,
 				CompactRevision: wresp.CompactRevision,
+				Canceled:        canceled,
 			}
 
 			if _, hasId := ids[wresp.WatchID]; !hasId {