OBSDOCS-1717: Update Alertmanager upstream version link for OCP 4.19 release

Author: eromanova97

modules/monitoring-configuring-alert-routing-default-platform-alerts.adoc

@@ -10,7 +10,7 @@ You can configure Alertmanager to send notifications to receive important alerts
 
 [NOTE]
 ====
-All features of a supported version of upstream Alertmanager are also supported in an {product-title} Alertmanager configuration. To check all the configuration options of a supported version of upstream Alertmanager, see link:https://prometheus.io/docs/alerting/0.27/configuration/[Alertmanager configuration] (Prometheus documentation).
+All features of a supported version of upstream Alertmanager are also supported in an {product-title} Alertmanager configuration. To check all the configuration options of a supported version of upstream Alertmanager, see link:https://prometheus.io/docs/alerting/0.28/configuration/[Alertmanager configuration] (Prometheus documentation).
 ====
 
 .Prerequisites

modules/monitoring-configuring-alert-routing-user-defined-alerts-secret.adoc

@@ -10,7 +10,7 @@ If you have enabled a separate instance of Alertmanager that is dedicated to use
 
 [NOTE]
 ====
-All features of a supported version of upstream Alertmanager are also supported in an {product-title} Alertmanager configuration. To check all the configuration options of a supported version of upstream Alertmanager, see link:https://prometheus.io/docs/alerting/0.27/configuration/[Alertmanager configuration] (Prometheus documentation).
+All features of a supported version of upstream Alertmanager are also supported in an {product-title} Alertmanager configuration. To check all the configuration options of a supported version of upstream Alertmanager, see link:https://prometheus.io/docs/alerting/0.28/configuration/[Alertmanager configuration] (Prometheus documentation).
 ====
 
 .Prerequisites