DOC: track status for stale comment in gbq docs
https://github.com/pydata/pandas/pull/5179 introduced the following warning

```
As of 10/10/13, there is a bug in Google’s API preventing result sets from being 
larger than 100,000 rows. A patch is scheduled for the week of 10/14/13.
```

@jacobschaer, is this still valid?
