derive `Clone` for `Certificate` #1809

Job	Run time
Check semver compatibility	55s
Validate external types appearing in public API	1m 36s
Documentation (stable)	1m 3s
Format & clippy	6m 52s
Documentation (nightly)	1m 13s
build (macOS-latest, stable)	3m 35s
Build rustls-cert-gen as a standalone package	28s
build (ubuntu-latest, stable)	6m 25s
build-windows	13m 13s
Measure coverage	6m 36s
build (ubuntu-latest, beta)	6m 58s
build (ubuntu-latest, nightly)	6m 41s
build (ubuntu-latest, stable 7 months ago)	6m 59s
	1h 2m 34s

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