feat: addressing review comments

Contributes to: event-integration/eventstreams-planning/12766
KIP Link:  https://cwiki.apache.org/confluence/display/KAFKA/KIP-1054%3A+Support+external+schemas+in+JSONConverte

Signed-off-by: Priyanka K U <[email protected]>

Author: priyankaku

connect/json/src/test/java/org/apache/kafka/connect/json/JsonConverterTest.java

@@ -982,7 +982,7 @@ public void testVersionRetrievedFromAppInfoParser() {
 
     @Test
     public void testSchemaContentIsNull() {
-        converter.configure(Map.of(JsonConverterConfig.SCHEMA_CONTENT_CONFIG, null), false);
+        converter.configure(Collections.singletonMap(JsonConverterConfig.SCHEMA_CONTENT_CONFIG, null), false);
         assertEquals(new SchemaAndValue(Schema.STRING_SCHEMA, "foo-bar-baz"), converter.toConnectData(TOPIC, "{ \"schema\": { \"type\": \"string\" }, \"payload\": \"foo-bar-baz\" }".getBytes()));
     }