Revert "Add producer.close()"

This reverts commit 139e078.

'Producer' object has no attribute 'close'
for confluent_kafka 2.4.0, the current version in
prompt-processing release.

python/lsst/ap/association/packageAlerts.py

@@ -306,7 +306,6 @@ def run(self,
 
         if self.config.doProduceAlerts:
             self.produceAlerts(alerts, visit, detector)
-            self.producer.close()
 
         if self.config.doWriteAlerts:
             with open(os.path.join(self.config.alertWriteLocation, f"{visit}_{detector}.avro"), "wb") as f: