all: remove dependency on proto v1

This does not remove all dependencies,
but all of the cases where it can now be implemented in terms of v2.

Change-Id: Idc5b0273f0d35c284bf2141eb9cce998692ceb15
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/184878
Reviewed-by: Herbie Ong <herbie@google.com>
diff --git a/compiler/protogen/protogen.go b/compiler/protogen/protogen.go
index 09264e6..0191e09 100644
--- a/compiler/protogen/protogen.go
+++ b/compiler/protogen/protogen.go
@@ -216,7 +216,7 @@
 	// .proto source file specifying the full import path of the Go package
 	// associated with this file.
 	//
-	//     option go_package = "github.com/golang/protobuf/ptypes/any";
+	//     option go_package = "google.golang.org/protobuf/types/known/anypb";
 	//
 	// Build systems which want to exert full control over import paths may
 	// specify M<filename>=<import_path> flags.