cleanup in FinNat #3028

Job	Run time
nix	2m 20s
opam-build (supported, ubuntu-latest)	10m 23s
quick-build (supported, ubuntu-latest)	3m 24s
build (supported)	3m 22s
opam-build (latest, ubuntu-latest)	4m 48s
quick-build (latest, ubuntu-latest)	3m 13s
opam-build (dev, ubuntu-latest)	4m 36s
build (latest)	3m 21s
quick-build (dev, ubuntu-latest)	3m 12s
build (dev, --warnings)	3m 16s
doc-timing	1m 41s
doc-dep-graphs	6m 54s
doc-alectryon	6m 55s
coqchk (supported)	2m 0s
doc-coqdoc	1m 39s
install (supported)	1m 39s
coqchk (latest)	1m 55s
install (latest)	1m 32s
coqchk (dev)	1m 44s
install (dev)	1m 51s
deploy-doc	1s
delete-artifacts	9s
	1h 9m 55s

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