multiboot2: fix wording #997

Job	Run time
build (stable) / rust	30s
build (nightly) / rust	45s
build (msrv) / rust	44s
build no_std (stable) / rust	20s
build no_std (stable) [w/o builder] / rust	17s
style (stable) / rust	28s
build no_std (stable) [Windows] / rust	2m 14s
style (msrv) / rust	22s
build no_std (msrv) / rust	22s
style (nightly) / rust	21s
tests with miri (nightly) / rust	1m 7s
build no_std (nightly) / rust	20s
	7m 50s

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