Decide on changing prior in fs2000.mod

https://github.com/DynareTeam/dynare/commit/b14cf33c8ffe936c3c3ad79846335e918be7fb77 changed the prior for rho in the integration tests to not have an asymptote. But this change was not ported to the fs2000.mod in the Dynare examples-folder. Following the discussion in #1401 (closed), we warn users against using such a prior. Therefore, I would propose to change the prior in the examplesmod-file as well. After all, it is an example, not a replication file.