This change is part of a migration of the Node examples from this
repository to the grpc/grpc-node repository, along with
grpc/grpc-node#2474. I replaced the files with references to the new
location instead of deleting them so that people following links in
existing external resources would find information about the new
location instead of an unhelpful 404 error. I discovered that even some
of the individual `.js` files are linked from other places, so to be
safe I performed this replacement on every file in the directory.
