Lwt_io.direct_access: fix grammar error
Lwt_io.direct_access: fix grammar error

ocsigen/lwt,gfxmonk/lwt,rgrinberg/lwt,rneswold/lwt,rgrinberg/lwt,c-cube/lwt,rgrinberg/lwt,mfp/lwt,fdopen/lwt,mfp/lwt,rneswold/lwt,rgrinberg/lwt,ocsigen/lwt,ocsigen/lwt,mirage/lwt,rneswold/lwt,gfxmonk/lwt,c-cube/lwt,fdopen/lwt,mirage/lwt,c-cube/lwt