multiboot2-header: talk about yanked versions in CHANGELOG.md #1066

Job	Run time
build (stable) / rust	12s
build (msrv) / rust	22s
build (nightly) / rust	32s
build no_std (stable) [w/o builder] / rust	12s
build no_std (stable) / rust	12s
style (stable) / rust	14s
build no_std (stable) [Windows] / rust	1m 14s
style (msrv) / rust	22s
build no_std (msrv) / rust	18s
tests with miri (nightly) / rust	1m 9s
build no_std (nightly) / rust	27s
style (nightly) / rust	32s
	5m 46s

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