fix torjan protobuf version

We could migrate to v2 version of protobuf interface now, but it would cause additional trouble. A quick fix is applied.

infra/conf/v4/trojan.go

@@ -6,7 +6,7 @@ import (
 	"strconv"
 	"syscall"
 
-	"google.golang.org/protobuf/proto"
+	"github.com/golang/protobuf/proto"
 
 	"github.com/v2fly/v2ray-core/v4/common/net"
 	"github.com/v2fly/v2ray-core/v4/common/protocol"