Remove known issue; fixed upstream

See confluentinc/confluent-kafka-python#1547 (comment).

README.md

@@ -155,10 +155,3 @@ consumer.assign(start)
 for message in consumer.consume(end[0].offset - start[0].offset, timeout=1):
     print(message.value())
 ```
-
-## Known Issues
-
-### confluent-kafka-python
-If you use confluent-kafka-python v2.1.0 or v2.1.1 with librdkafka v2.1.1 you will encounter a segmentation fault when subscribed to unavailable topics.
-
-Please refer to [the confluent-kafka-python github issue](https://github.com/confluentinc/confluent-kafka-python/issues/1547) for updates on the issue.