Typo in 7.7.2.2-p4

```
A portion of paragraph 4 of 7.7.2.2 (The upc_thread_info function) currently 
reads:

> If the flag is set for a particular region is set in
> the probablyCastable field ....

One should remove the first of the two instances of the phrase "is set".
```

Original issue reported on code.google.com by `phhargr...@lbl.gov` on 19 Apr 2014 at 12:31
