Fix instance cycle in Homotopy.HSpace.Core #1516

Job	Run time
nix	3m 53s
build (supported)	4m 24s
build (latest)	4m 31s
build (dev, --warnings)	4m 31s
quick-build (supported, ubuntu-latest)	3m 33s
quick-build (latest, ubuntu-latest)	3m 31s
quick-build (dev, ubuntu-latest)	4m 7s
opam-build (supported, ubuntu-latest)	6m 45s
opam-build (8.17, ubuntu-latest)	7m 36s
opam-build (latest, ubuntu-latest)	5m 45s
opam-build (dev, ubuntu-latest)	5m 43s
doc-timing	1m 44s
doc-coqdoc	1m 35s
doc-alectryon	18m 15s
coqchk (supported)	1m 56s
coqchk (latest)	2m 28s
coqchk (dev)	1m 53s
doc-dep-graphs	10m 43s
install (supported)	1m 49s
install (latest)	1m 26s
install (dev)	1m 31s
deploy-doc	0s
delete-artifacts	7s
	1h 37m 46s

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