Support `containers` version `0.8`.

[jonathanknowles]

Version 0.8 of the containers package has been released. The quickcheck-instances package currently has an upper bound of < 0.8:

qc-instances/quickcheck-instances.cabal

Lines 88 to 92 in b853ddf

	build-depends:
	, array >=0.5.3.0 && <0.6
	, bytestring >=0.10.8.2 && <0.13
	, case-insensitive >=1.2.0.11 && <1.3
	, containers >=0.6.0.1 && <0.8