Fix MCMC maps for Sherpa 2.2.16
Following up from !75994 (merged), make sure Sherpa 2.2.16 is handled properly. Currently, the logic would return Sherpa 2.2.1 and cause a crash because it's not supported in the latest CDI files for GN2, as observed by @maharris.
Tagging @bdong who authored the linked MR.