fix: remove HEADER_LENGTH in decode because of discard

protocol/dubbo/impl/codec.go

@@ -157,7 +157,7 @@ func (c *ProtocolCodec) Decode(p *DubboPackage) error {
 			return err
 		}
 	}
-	if c.reader.Size() < p.GetBodyLen()+HEADER_LENGTH {
+	if c.reader.Size() < p.GetBodyLen() { // discard header, header length is not necessary
 		return hessian.ErrBodyNotEnough
 	}
 	body, err := c.reader.Peek(p.GetBodyLen())