Fix a reference.

This is the first case a reference gets removed. I sincerely hope our
scripts are able to deal with this!

Thanks to Kestutis Cesnavicius
http://stacks.math.columbia.edu/tag/0A3V#comment-722
http://stacks.math.columbia.edu/tag/05TN#comment-723
http://stacks.math.columbia.edu/tag/0AF9#comment-727