[FLINK-34996][Connectors/Kafka] Use UserCodeClassLoader to instantiate Deserializer.

Author: hugogu

flink-connector-kafka/src/main/java/org/apache/flink/connector/kafka/source/reader/deserializer/KafkaValueOnlyDeserializerWrapper.java

@@ -65,7 +65,7 @@ public void open(DeserializationSchema.InitializationContext context) throws Exc
                             InstantiationUtil.instantiate(
                                     deserializerClass.getName(),
                                     Deserializer.class,
-                                    getClass().getClassLoader());
+                                    userCodeClassLoader);
 
             if (deserializer instanceof Configurable) {
                 ((Configurable) deserializer).configure(config);