crl: avoid markdown footnotes #1440

Job	Run time
Validate external types appearing in public API	1m 28s
Documentation (stable)	1m 7s
Documentation (nightly)	1m 6s
Build rustls-cert-gen as a standalone package	39s
build (macOS-latest, stable)	34s
build-windows	9m 26s
build (ubuntu-latest, stable)	5m 42s
build (ubuntu-latest, beta)	5m 55s
Measure coverage	46s
build (ubuntu-latest, nightly)	5m 55s
Format & clippy	5m 23s
build (ubuntu-latest, stable 7 months ago)	45s
Check semver compatibility	54s
	39m 40s

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