Fix link to Custom Threshold rules (#2931)

It seems like this was copied from the line above and not updated.

Author: gtback

solutions/observability/incident-management/create-manage-rules.md

@@ -29,7 +29,7 @@ Learn more about Observability rules and how to create them:
 | --- | --- | --- |
 | AIOps | [Anomaly detection](/solutions/observability/incident-management/create-an-apm-anomaly-rule.md) | Anomalies match specific conditions. |
 | APM | [APM anomaly](/solutions/observability/incident-management/create-an-apm-anomaly-rule.md) | The latency, throughput, or failed transaction rate of a service is abnormal. |
-| Observability | [Custom threshold](/solutions/observability/incident-management/create-an-apm-anomaly-rule.md) | An Observability data type reaches or exceeds a given value. |
+| Observability | [Custom threshold](/solutions/observability/incident-management/create-custom-threshold-rule.md) | An Observability data type reaches or exceeds a given value. |
 | Data set quality | [Degraded docs](/solutions/observability/incident-management/create-a-degraded-docs-rule.md) | The percentage of degraded documents for a data view exceeds a threshold |
 | Stack | [{{es}} query](/solutions/observability/incident-management/create-an-elasticsearch-query-rule.md) | Matches are found during the latest query run. |
 | APM | [Error count threshold](/solutions/observability/incident-management/create-an-error-count-threshold-rule.md) | The number of errors in a service exceeds a defined threshold. |
@@ -100,4 +100,4 @@ To temporarily suppress notifications for *all* rules, create a [maintenance win
 
 To import and export rules, use [{{saved-objects-app}}](/explore-analyze/find-and-organize.md).
 
-Rules are disabled on export. You are prompted to re-enable the rule on successful import.
+Rules are disabled on export. You are prompted to re-enable the rule on successful import.