kube-prometheus: Rename DeadMansSwitch to Watchdog

jsonnet/kube-prometheus/alerts/general.libsonnet

@@ -16,9 +16,15 @@
             },
           },
           {
-            alert: 'DeadMansSwitch',
+            alert: 'Watchdog',
             annotations: {
-              message: 'This is a DeadMansSwitch meant to ensure that the entire alerting pipeline is functional.',
+              message: |||
+                This is an alert meant to ensure that the entire alerting pipeline is functional.
+                This alert is always firing, therefore it should always be firing in Alertmanager
+                and always fire against a receiver. There are integrations with various notification
+                mechanisms that send a notification when this alert is not firing. For example the
+                "DeadMansSnitch" integration in PagerDuty.
+              |||,
             },
             expr: 'vector(1)',
             labels: {