Use voltha-protos version 4.0.2
Bump major version of voltha-lib-go to 4.0.0 as this change results
in incompatible API version compared to previous version

Change-Id: I1def58361fb1d85f07d6948ebf1ffb7a92eb0d4c
diff --git a/pkg/grpc/server.go b/pkg/grpc/server.go
index f5f9550..ed2d5ec 100644
--- a/pkg/grpc/server.go
+++ b/pkg/grpc/server.go
@@ -19,7 +19,7 @@
 	"context"
 	grpc_middleware "github.com/grpc-ecosystem/go-grpc-middleware"
 	grpc_opentracing "github.com/grpc-ecosystem/go-grpc-middleware/tracing/opentracing"
-	"github.com/opencord/voltha-lib-go/v3/pkg/log"
+	"github.com/opencord/voltha-lib-go/v4/pkg/log"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/credentials"