Updated Prometheus Operator documentation (robusta-dev#670)

Co-authored-by: Pavan <pavangudiwada@users.noreply.github.com>

docs/user-guide/alert-manager.rst

@@ -72,10 +72,9 @@ Add custom AlertManager, Grafana or Prometheus in ``generated_values.yaml``.
 
 Prometheus Operator
 -----------------------
-If you are using a Prometheus Operator that was **not** installed with Robusta, you should define a `manually-managed secret <https://github.com/prometheus-operator/prometheus-operator/blob/master/Documentation/user-guides/alerting.md#manually-managed-secret>`_
-that sends alerts to Robusta by webhook.
+If you are using a Prometheus Operator that was **not** installed with Robusta, you should define a `manually-managed secret <https://github.com/prometheus-operator/prometheus-operator/blob/main/Documentation/user-guides/alerting.md#using-a-kubernetes-secret>`_. Your Prometheus Operator uses this secret to sends alerts to Robusta by webhook.
 
-Follow the `instructions in the Prometheus Operator documentation <https://github.com/prometheus-operator/prometheus-operator/blob/master/Documentation/user-guides/alerting.md#manually-managed-secret>`_, using the above configuration for alertmanager.yaml.
+AlertManager pushes alerts to Robusta. Follow the instructions in the `Prometheus Operator documentation <https://github.com/prometheus-operator/prometheus-operator/blob/main/Documentation/user-guides/alerting.md#managing-alertmanager-configuration>`_, using the above configuration to configure alertmanager.yaml.
 
 An alternative is to configure an AlertmanagerConfig CRD, but this is **not** recommended as it `will only forward alerts from one namespace <https://github.com/prometheus-operator/prometheus-operator/issues/3750>`_.