fix and update alectryon #3950

Job	Run time
opam-build (9.1, ubuntu-latest)	4m 15s
opam-build (9.0, ubuntu-latest)	4m 8s
nix	2m 10s
build (9.0)	3m 12s
opam-build (dev, ubuntu-latest)	4m 17s
build (9.1)	3m 21s
quick-build (9.0, ubuntu-latest)	3m 6s
quick-build (dev, ubuntu-latest)	3m 26s
quick-build (9.1, ubuntu-latest)	3m 8s
build (dev, --warnings)	3m 45s
doc-dep-graphs	7m 1s
doc-alectryon	14m 27s
doc-coqdoc	1m 32s
install (dev)	1m 49s
install (9.1)	1m 35s
install (9.0)	1m 38s
doc-timing	1m 49s
coqchk (9.1)	1m 37s
coqchk (dev)	2m 3s
coqchk (9.0)	1m 53s
deploy-doc	0s
delete-artifacts	7s
	1h 10m 19s

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