gnu: haskell-xyz.scm: Correctly hide packages.

* gnu/packages/haskell-xyz.scm (ghc-attoparsec-bootstrap,
ghc-integer-logarithms-bootstrap, ghc-scientific-bootstrap,
ghc-semigroups-bootstrap, ghc-unordered-containers-bootstrap,
ghc-wcwidth-bootstrap)[properties]: Fix typo, make 'hidden?' a tuple.