remove RupicolaCrypto.Low #703

Job	Run time
install (dev, 4.11.1, ubuntu-latest)	1h 3m 2s
install (dev, 4.11.1, macos-latest)	48m 9s
install (dev, 4.11.1, windows-latest, opam-repository-mingw: https://github.com/ocaml-opam/opam-r...	1h 38m 12s
install (8.18.0, 4.11.1, ubuntu-latest)	40m 19s
install (8.18.0, 4.11.1, macos-latest)	48m 18s
install (8.18.0, 4.11.1, windows-latest, opam-repository-mingw: https://github.com/ocaml-opam/opa...	2h 11m 15s
install (8.17.0, 4.11.1, ubuntu-latest)	1h 7m 44s
install (8.17.0, 4.11.1, macos-latest)	59m 31s
install (8.17.0, 4.11.1, windows-latest, opam-repository-mingw: https://github.com/ocaml-opam/opa...	2h 36m 37s
	11h 53m 7s

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