support QuickCheck-2.16

[fraser-iohk]

Fixes breaking build when using QuickCheck-2.16 due to clashing Some now exported from Test.QuickCheck

Checklist:

• Check source-code formatting is consistent

[ch1bo]

Tests failing with

src/Test/QuickCheck/StateModel/Variables.hs:34:1: error: [-Wdodgy-imports, Werror=dodgy-imports]
    Module ‘Test.QuickCheck’ does not export ‘Some(..)’
   |
34 | import Test.QuickCheck as QC hiding (Some (..))
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Error: cabal: Failed to build quickcheck-dynamic-4.0.0 (which is required by
test:quickcheck-dynamic-test from quickcheck-dynamic-4.0.0).

I'd suggest to do explicit imports. Making this qualified would also work, but that would lead to a bigger diff.

[ch1bo]

Changes look good. Not sure against which version of QuickCheck CI builds right now and we seem not to have version bounds on that dependency..