Mark set_size and set_fold as TC opaque

2 jobs for !329 with finite_sets_2 in 9 minutes and 36 seconds (queued for 9 seconds)
detached
Status Name Job ID Coverage
  Build
passed build-coq.8.10.2 #152647
fp

00:06:08

passed build-coq.8.13.2-mr #152646
fp

00:09:36