Bump quickcheck dev dependency

Author: garyb

bower.json

@@ -30,7 +30,7 @@
     "purescript-unsafe-coerce": "^4.0.0"
   },
   "devDependencies": {
-    "purescript-quickcheck": "^5.0.0",
+    "purescript-quickcheck": "^6.0.0",
     "purescript-minibench": "^2.0.0",
     "purescript-console": "^4.0.0",
     "purescript-assert": "^4.0.0"