CRAN MASS_7.3-39 was uploaded twice, so use the newer checksum

The two dates are:

Packaged: 2015-02-20 08:29:38 UTC; ripley
Packaged: 2015-02-24 10:34:20 UTC; ripley

There were with changes to tests/Examples/MASS-Ex.Rout.save,
but the rest of the code seems unaffected.