MINOR: Increase timeout in log4j system test to avoid transient failures (#5658)

Reviewers: Ismael Juma <ismael@juma.me.uk>

tests/kafkatest/tests/tools/log4j_appender_test.py

@@ -66,7 +66,7 @@ class Log4jAppenderTest(Test):
 
     def start_consumer(self):
         self.consumer = ConsoleConsumer(self.test_context, num_nodes=self.num_brokers, kafka=self.kafka, topic=TOPIC,
-                                        consumer_timeout_ms=1000,
+                                        consumer_timeout_ms=10000,
                                         message_validator=self.custom_message_validator)
         self.consumer.start()