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Mention JDK `17+` requirement in README #602

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Run time

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Job	Run time
build (3.8.8, 17, ubuntu-latest)	5m 37s
build (3.8.8, 17, windows-latest)	8m 6s
build (3.8.8, 21, ubuntu-latest)	5m 51s
build (3.8.8, 21, windows-latest)	7m 4s
build (3.9.9, 17, ubuntu-latest)	5m 48s
build (3.9.9, 17, windows-latest)	9m 18s
build (3.9.9, 21, ubuntu-latest)	5m 56s
build (3.9.9, 21, windows-latest)	7m 59s
	55m 39s