io_uring/waitid: always prune wait queue entry in io_waitid_wait()

In the Linux kernel, the following vulnerability has been resolved: io_uring/waitid: always prune wait queue entry in io_waitid_wait() For a successful return, always remove our entry from the wait queue entry list. Previously this was skipped if a cancelation was in progress, but this can race with another invocation of the wait queue entry callback.