Fix date-time failure case

It has to fail on date-time.

test/inputs/schema/date-time.1.fail.date-time.json

@@ -1,7 +1,7 @@
 {
   "date": "In the year of the lord 1985 on April the 12th",
   "time": "23:20:50.52Z",
-  "date-time": "1985-04-12T23:20:50.52Z",
+  "date-time": "On the 1985-04-12 at 23:20:50.52Z",
   "union-array": ["1985-04-12", "23:20:50.52Z"],
   "complex-union-array": ["1985-04-12T23:20:50.52Z", "foo", 123]
 }