unix: remove unneeded TODO note

It's already documented in
http://docs.libuv.org/en/v1.x/stream.html#c.uv_accept

PR-URL: https://github.com/libuv/libuv/pull/916
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Imran Iqbal <imran@imraniqbal.org>

src/unix/stream.c

@@ -571,7 +571,6 @@ void uv__server_io(uv_loop_t* loop, uv__io_t* w, unsigned int events) {
 int uv_accept(uv_stream_t* server, uv_stream_t* client) {
   int err;
 
-  /* TODO document this */
   assert(server->loop == client->loop);
 
   if (server->accepted_fd == -1)