zlib-enum.cabal: drop 'test' flag in favour of Cabal test support

Now tests can be enabled as 'runhaskell Setu --enable-tests'.

Eases automatic packaging in downstream distibutions.

Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
Merge pull request #10 from trofi/master

zlib-enum.cabal: drop 'test' flag in favour of Cabal test support