Update dag docs

DAGs.md

@@ -204,15 +204,17 @@ Checks for DAGs that have silenced Slack alerts which may need to be turned back
 on.
 
 When a DAG has known failures, it can be ommitted from Slack error reporting by adding
-an entry to the `silenced_slack_alerts` Airflow variable. This is a dictionary where the
-key is the `dag_id` of the affected DAG, and the value is the URL of a GitHub issue
-tracking the error.
-
-The `check_silenced_alert` DAG iterates over the entries in the `silenced_slack_alerts`
-configuration and verifies that the associated GitHub issues are still open. If an issue
-has been closed, it is assumed that the DAG should have Slack reporting reenabled, and
-an alert is sent to prompt manual update of the configuration. This prevents developers
-from forgetting to reenable Slack reporting after the issue has been resolved.
+an entry to the `silenced_slack_notifications` Airflow variable. This is a dictionary
+where thekey is the `dag_id` of the affected DAG, and the value is a list of
+SilencedSlackNotifications (which map silenced notifications to GitHub URLs) for that
+DAG.
+
+The `check_silenced_dags` DAG iterates over the entries in the
+`silenced_slack_notifications` configuration and verifies that the associated GitHub
+issues are still open. If an issue has been closed, it is assumed that the DAG should
+have Slack reporting reenabled, and an alert is sent to prompt manual update of the
+configuration. This prevents developers from forgetting to reenable Slack reporting
+after the issue has been resolved.
 
 The DAG runs weekly.