tests/Displayable.hs: use default instances from N.M.C.Types
tests/Displayable.hs: use default instances from N.M.C.Types

Signed-off-by: Joachim Fasting <joachim.fasting@gmail.com>

Signed-off-by: Ben Sinclair <fb4a9eda4dc9958876c50108c070f6fd29c0fb74@gmail.com>
beni55/libmpd-haskell,sol/libmpd-haskell