unix: remove FSEventStreamFlushSync() call

This call, in the context of file watching, appears to trigger
assertion warnings on some macOS configurations.

Refs: https://github.com/nodejs/node/issues/854
Fixes: https://github.com/libuv/libuv/issues/1334
PR-URL: https://github.com/libuv/libuv/pull/1349
Reviewed-By: Fedor Indutny <fedor.indutny@gmail.com>
Reviewed-By: Saúl Ibarra Corretgé <saghul@gmail.com>

src/unix/fsevents.c

@@ -378,9 +378,6 @@ static void uv__fsevents_destroy_stream(uv_loop_t* loop) {
   if (state->fsevent_stream == NULL)
     return;
 
-  /* Flush all accumulated events */
-  pFSEventStreamFlushSync(state->fsevent_stream);
-
   /* Stop emitting events */
   pFSEventStreamStop(state->fsevent_stream);