bump alertmanager dep

Signed-off-by: drfaust92 <[email protected]>

charts/prometheus/Chart.yaml

@@ -1,7 +1,7 @@
 apiVersion: v2
 name: prometheus
 appVersion: v2.50.1
-version: 25.15.0
+version: 25.16.0
 kubeVersion: ">=1.19.0-0"
 description: Prometheus is a monitoring system and time series database.
 home: https://prometheus.io/
@@ -26,7 +26,7 @@ maintainers:
 type: application
 dependencies:
   - name: alertmanager
-    version: "1.8.*"
+    version: "1.9.*"
     repository: https://prometheus-community.github.io/helm-charts
     condition: alertmanager.enabled
   - name: kube-state-metrics