modified aeDeleteFileEvent() function

modified aeDeleteFileEvent() function:
```c
void aeDeleteFileEvent(aeEventLoop *eventLoop, int fd, int mask)
{
    if (fd >= eventLoop->setsize) return;
    aeFileEvent *fe = &eventLoop->events[fd];

    if (fe->mask == AE_NONE) return;

    aeApiDelEvent(eventLoop, fd, mask);

    fe->mask = fe->mask & (~mask);
    if (fd == eventLoop->maxfd && fe->mask == AE_NONE) {
        /* Update the max fd */
        int j;

        for (j = eventLoop->maxfd-1; j >= 0; j--)
            if (eventLoop->events[j].mask != AE_NONE) break;
        eventLoop->maxfd = j;
    }
}
```