use new newJsonMapper style for creating ObjectMapper

Author: sigpwned

src/test/java/tools/jackson/databind/jsontype/SealedTypesWithSubtypesTest.java

@@ -183,7 +183,7 @@ public POJOWrapper(Sub sub1, Sub sub2) {
     /**********************************************************************
      */
 
-    private final ObjectMapper MAPPER = new ObjectMapper();
+    private final ObjectMapper MAPPER = newJsonMapper();
 
     @Test
     public void testPropertyWithSubtypes() throws Exception

src/test/java/tools/jackson/databind/jsontype/SealedTypesWithTypedSerializationTest.java

@@ -84,7 +84,7 @@ public class B extends Super {}
     /**********************************************************
      */
 
-    private final ObjectMapper MAPPER = new ObjectMapper();
+    private final ObjectMapper MAPPER = newJsonMapper();
 
     /**
      * First things first, let's ensure we can serialize using