Drop support for GHC < 8.6 #222

Job	Run time
i386	4m 25s
arm (arm32v7)	3m 56s
darwin_arm (self-hosted, macOS, ARM64, 8.10.7)	1m 0s
arm (arm64v8)	3m 14s
build (ubuntu-latest, 8.6, 3.8.1.0)	5m 25s
darwin_arm (self-hosted, macOS, ARM64, 9.2.6)	1m 4s
build (ubuntu-latest, 8.8, 3.8.1.0)	5m 31s
darwin_arm (self-hosted, macOS, ARM64, 9.4.4)	54s
build (ubuntu-latest, 8.10, 3.8.1.0)	5m 40s
build (ubuntu-latest, 9.0, 3.8.1.0)	5m 18s
build (ubuntu-latest, 9.2, 3.8.1.0)	3m 51s
build (ubuntu-latest, 9.4, 3.8.1.0)	4m 28s
build (ubuntu-latest, 9.6, 3.8.1.0)	3m 3s
build (ubuntu-latest, 9.8, 3.8.1.0)	7m 2s
build (macOS-latest, 9.4, 3.8.1.0)	23m 59s
build (macOS-latest, 9.6, 3.8.1.0)	11m 5s
build (windows-latest, 9.4, 3.8.1.0)	18m 58s
build (windows-latest, 9.6, 3.8.1.0)	15m 18s
	2h 4m 11s

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