Remove invalid draft6 test using draft7 constructs

Resolves #535

Author: jimmylewis

tests/draft6/contains.json

@@ -125,26 +125,5 @@
                 "valid": false
             }
         ]
-    },
-    {
-        "description": "contains with false if subschema",
-        "schema": {
-            "contains": {
-                "if": false,
-                "else": true
-            }
-        },
-        "tests": [
-            {
-                "description": "any non-empty array is valid",
-                "data": ["foo"],
-                "valid": true
-            },
-            {
-                "description": "empty array is invalid",
-                "data": [],
-                "valid": false
-            }
-        ]
     }
 ]