haskell-yesod-static: disable the yesod-static test suite

It produces a strange error:

  Running 1 test suites...
  Test suite tests: RUNNING...

  /nix/store/gwm3821513h0jwcgxr73r3ay90shaq7r-haskell-base64-bytestring-ghc7.6.3-1.0.0.1/bin/../lib/ghc-7.6.3/package.conf.d/base64-bytestring-1.0.0.1.installedconf:1:19272:
      Not in scope: `main'
      Perhaps you meant `min' (imported from Prelude)
  ...

I'm not sure what this means.