doc: fix typo in package networktype (#4508)
doc: fix typo in package networktype (#4508)


stanley-cheung/grpc-go,dfawley/grpc-go,menghanl/grpc-go,menghanl/grpc-go,stanley-cheung/grpc-go,dfawley/grpc-go,grpc/grpc-go,grpc/grpc-go