CI: cosmetics: remove excluded version 8.4 which isn't included in ma… #910

Job	Run time
centos7	3m 19s
arm (arm32v7)	2m 41s
build (ubuntu-22.04, 9.8)	2m 37s
arm (arm64v8)	2m 21s
fedora37	4m 28s
freebsd (self-hosted, FreeBSD, X64, 9.4)	1m 37s
build (ubuntu-22.04, 9.6)	2m 33s
freebsd (self-hosted, FreeBSD, X64, 9.6)	1m 45s
i386	3m 28s
build (ubuntu-22.04, 9.4)	4m 3s
build (ubuntu-22.04, 9.2)	2m 54s
build (ubuntu-22.04, 9.0)	4m 29s
build (ubuntu-22.04, 8.10)	4m 23s
build (ubuntu-22.04, 8.8)	4m 29s
build (ubuntu-22.04, 8.6)	4m 34s
build (macOS-latest, 9.8)	3m 58s
build (macOS-latest, 9.6)	4m 8s
build (macOS-latest, 9.4)	4m 6s
build (macOS-latest, 9.2)	2m 56s
	1h 4m 49s

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