fix flaky test serializeDateTimeProperty

Author: xinying7

modules/swagger-core/src/test/java/io/swagger/v3/core/serialization/properties/PropertySerializationTest.java

@@ -68,8 +68,11 @@ public void deserializeDateProperty() throws IOException {
     @Test(description = "it should serialize a DateTimeProperty")
     public void serializeDateTimeProperty() throws IOException {
         final DateTimeSchema p = new DateTimeSchema();
-        final String json = "{\"type\":\"string\",\"format\":\"date-time\"}";
-        assertEquals(m.writeValueAsString(p), json);
+        final String json1 = "{\"type\":\"string\",\"format\":\"date-time\"}";
+        String json2 = m.writeValueAsString(p);
+        JSONObject jsonObj1 = new JSONObject(json1);
+        JSONObject jsonObj2 = new JSONObject(json2);
+        JSONAssert.assertEquals(jsonObj1, jsonObj2, true);
     }
 
     @Test(description = "it should deserialize a DateTimeProperty")