otter: Mark broken

Build hangs an hits the hydra time limit:
http://hydra.nixos.org/build/34897110

pkgs/applications/science/logic/otter/default.nix

···
     license = stdenv.lib.licenses.publicDomain ;
     maintainers = [stdenv.lib.maintainers.raskin];
     platforms = stdenv.lib.platforms.linux;
+    broken = true;
   };
 }