Briefly mention Rocq in INSTALL.md #3873

Job	Run time
opam-build (supported, ubuntu-latest)	5m 24s
quick-build (supported, ubuntu-latest)	4m 0s
quick-build (dev, ubuntu-latest)	3m 21s
opam-build (latest, ubuntu-latest)	4m 14s
nix	2m 17s
opam-build (dev, ubuntu-latest)	4m 14s
build (latest)	3m 34s
quick-build (latest, ubuntu-latest)	3m 32s
build (supported)	3m 57s
build (dev, --warnings)	3m 43s
doc-alectryon	15m 29s
doc-dep-graphs	7m 33s
doc-timing	1m 47s
coqchk (supported)	2m 19s
coqchk (dev)	1m 41s
doc-coqdoc	1m 55s
coqchk (latest)	2m 18s
install (latest)	1m 42s
install (supported)	1m 49s
install (dev)	1m 39s
deploy-doc	0s
delete-artifacts	6s
	1h 16m 34s

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