small style tweaks in Loops.v #2968

Job	Run time
build (supported)	3m 32s
opam-build (supported, ubuntu-latest)	4m 53s
build (latest)	3m 22s
quick-build (supported, ubuntu-latest)	3m 19s
opam-build (latest, ubuntu-latest)	4m 45s
build (dev, --warnings)	3m 33s
opam-build (dev, ubuntu-latest)	4m 28s
quick-build (latest, ubuntu-latest)	3m 16s
nix	2m 8s
quick-build (dev, ubuntu-latest)	3m 9s
doc-dep-graphs	7m 30s
doc-coqdoc	1m 39s
doc-alectryon	15m 0s
coqchk (supported)	2m 10s
doc-timing	1m 35s
install (supported)	1m 41s
coqchk (latest)	2m 0s
install (latest)	1m 34s
coqchk (dev)	1m 56s
install (dev)	1m 48s
deploy-doc	0s
delete-artifacts	5s
	1h 13m 23s

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