Remove timing assertion from oneshot::send_before_recv_timeout

Author: JonathanBrouwer

library/std/tests/sync/oneshot.rs

@@ -97,7 +97,9 @@ fn send_before_recv_timeout() {
         _ => panic!("expected Ok(22)"),
     }
 
-    assert!(start.elapsed() < timeout);
+    // FIXME(#152648): There previously was a timing assertion here.
+    // This was removed, because under load there's no guarantee that the main thread is
+    // scheduled and run before `timeout` expires
 }
 
 #[test]