Change version to 1.42.0-dev (#4793)
Change version to 1.42.0-dev (#4793)


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