private/piecestore: bump the streaming based BF size threshold

This is a workaround for a production issue, where we generated bloom filters with max size 4100000, which may end with a packet with size of 4100003.

It would be better to make this one configurable, but right now, we can bump it quickly.

Change-Id: I025889916609775c2ad4e52dc21fb643d653356e

private/piecestore/client.go

@@ -28,7 +28,7 @@ var errMessageTimeout = errors.New("message timeout")
 const (
 	// retainMessageLimit defines the max size which can be sent via normal request/response protocol.
 	// 4MB is the absolute max, defined by DRPC RPC, but we need a few bytes for protobuf overhead / filter header.
-	retainMessageLimit = 4100000
+	retainMessageLimit = 4100050
 )
 
 var (