Lwt_unix.auto_yield: fix documentation grammar
Lwt_unix.auto_yield: fix documentation grammar

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