fin_sets: add missing Params instance for `set_map`

Noticed from VERY slow rewrites.
2 jobs for !328 with finite_sets in 4 minutes and 51 seconds (queued for 8 seconds)
detached
Status Name Job ID Coverage
  Build
passed build-coq.8.10.2 #148525
fp

00:04:51

passed build-coq.8.13.2-mr #148524
fp

00:04:26