linked-list: Supress HLint's suggestions to reduce duplication.
linked-list: Supress HLint's suggestions to reduce duplication.

The following suggestions would probably make the tests
shorter, but harder to read:

```
./test/Tests.hs:16:7: Suggestion: Reduce duplication
Found:
  deque <- mkDeque
  push deque 'a'
  push deque 'b'
Why not:
  Combine with ./test/Tests.hs:23:7

./test/Tests.hs:16:7: Suggestion: Reduce duplication
Found:
  deque <- mkDeque
  push deque 'a'
  push deque 'b'
  pop deque `shouldReturn` Just 'b'
Why not:
  Combine with ./test/Tests.hs:44:7

./test/Tests.hs:30:7: Suggestion: Reduce duplication
Found:
  deque <- mkDeque
  unshift deque 'a'
  unshift deque 'b'
Why not:
  Combine with ./test/Tests.hs:37:7

3 hints
```

It is not clear why, but `hlint` doesn't supresses the suggestions
if we use `{-# ANN specs ...`, only with `{-# ANN module ...`.

exercism/xhaskell