Update distribution conf by removing unused variable

Author: JulienPeloton

conf_cluster/fink.conf.distribution_cluster

@@ -70,6 +70,3 @@ FINK_PRODUCER_JAAS="./fink_kafka_producer_jaas.conf"
 # Fink test Consumer
 FINK_TEST_CONSUMER_JAAS="${FINK_HOME}/conf/fink_kafka_consumer_jaas.conf"
 FINK_TEST_CONSUMER_JAAS="./fink_kafka_consumer_jaas.conf"
-
-# Slack channels to send automatic alerts
-SLACK_CHANNELS="${FINK_HOME}/conf/slack_channels.txt"