change XContentFactory to MediaTypeRegistry builder in MLRegisterMode…

…lInputTest class

Signed-off-by: Bhavana Ramaram <rbhavna@amazon.com>

common/src/test/java/org/opensearch/ml/common/transport/register/MLRegisterModelInputTest.java

@@ -277,7 +277,7 @@ public void testMCorrInput() throws IOException {
                 .deployModel(true)
                 .modelNodeIds(new String[]{"modelNodeIds" })
                 .build();
-        XContentBuilder builder = XContentFactory.jsonBuilder();
+        XContentBuilder builder = MediaTypeRegistry.contentBuilder(XContentType.JSON);
         mcorrInput.toXContent(builder, ToXContent.EMPTY_PARAMS);
         String jsonStr = builder.toString();
         assertEquals(testString, jsonStr);