cleanup in FinNat #3026

Job	Run time
quick-build (supported, ubuntu-latest)	1m 48s
quick-build (latest, ubuntu-latest)	3m 11s
nix	2m 23s
quick-build (dev, ubuntu-latest)	3m 16s
opam-build (supported, ubuntu-latest)	3m 54s
build (supported)	1m 51s
opam-build (latest, ubuntu-latest)	4m 42s
build (latest)	3m 27s
opam-build (dev, ubuntu-latest)	4m 29s
build (dev, --warnings)	3m 22s
doc-coqdoc	0s
coqchk	0s
doc-alectryon	0s
doc-dep-graphs	0s
doc-timing	0s
install	0s
deploy-doc	0s
delete-artifacts	9s
	32m 32s

Provide feedback