remove questionable sched_yield - probably left over from debugging

This commit was SVN r8457.

ompi/mca/pml/ob1/pml_ob1_sendreq.c

@@ -999,9 +999,6 @@ void mca_pml_ob1_send_request_put(
             orte_errmgr.abort();
         }
     }
-#ifdef HAVE_SCHED_YIELD
-    sched_yield();
-#endif
 }