"old release" banner needs z-index: 1 or equivalent

Going to

https://cxc.harvard.edu/ciao4.14/download/

I see that the "This page is for the CIAO 4.14 release. Please ..." banner is hidden once you scroll down. An initial tests suggests that adding

```
z-index: 1;
```

to the CSS fixes this. Need to look at a bit more to check.