Modify the assert to accept any instance of AvroCoder, including subclasses. (#34843) (#34850)

Co-authored-by: fozzie15 <[email protected]>

Author: chamikaramj

sdks/java/io/kafka/src/main/java/org/apache/beam/sdk/io/kafka/KafkaReadSchemaTransformProvider.java

@@ -196,7 +196,7 @@ public PCollectionRowTuple expand(PCollectionRowTuple input) {
         PCollection<GenericRecord> kafkaValues =
             input.getPipeline().apply(kafkaRead.withoutMetadata()).apply(Values.create());
 
-        assert kafkaValues.getCoder().getClass() == AvroCoder.class;
+        assert kafkaValues.getCoder() instanceof AvroCoder;
         AvroCoder<GenericRecord> coder = (AvroCoder<GenericRecord>) kafkaValues.getCoder();
         kafkaValues = kafkaValues.setCoder(AvroUtils.schemaCoder(coder.getSchema()));
         return PCollectionRowTuple.of("output", kafkaValues.apply(Convert.toRows()));