Fix bootstrap server addresses and add comment.

Author: salmany

managedkafka/managedkafka_create_connector_mirrormaker2_source/main.tf

@@ -106,8 +106,10 @@ resource "google_managed_kafka_connector" "default" {
     "source.cluster.alias"             = "source"
     "target.cluster.alias"             = "target"
     "topics"                           = ".*" # Replicate all topics from the source
-    "source.cluster.bootstrap.servers" = google_managed_kafka_cluster.source.gcp_config[0].access_config[0].network_configs[0].bootstrap_servers
-    "target.cluster.bootstrap.servers" = google_managed_kafka_cluster.target.gcp_config[0].access_config[0].network_configs[0].bootstrap_servers
+    # The value for bootstrap.servers is a comma-separated list of hostname:port pairs for one
+    # or more Kafka brokers in the source/target cluster.
+    "source.cluster.bootstrap.servers" = "source_cluster_dns"
+    "target.cluster.bootstrap.servers" = "target_cluster_dns"
     # Using a replication policy is a good practice to identify mirrored topics.
     # It prefixes the topic name with the source alias (e.g., "source.my-topic").
     "replication.policy.class" = "org.apache.kafka.connect.mirror.DefaultReplicationPolicy"