OBSDOCS-1321: default thanos-ruler retention time should be 24h, not 15d in api.md

Author: eromanova97

observability/monitoring/config-map-reference-for-the-cluster-monitoring-operator.adoc

@@ -734,7 +734,7 @@ Appears in: link:#userworkloadconfiguration[UserWorkloadConfiguration]
 
 |resources|*v1.ResourceRequirements|Defines resource requests and limits for the Alertmanager container.
 
-|retention|string|Defines the duration for which Prometheus retains data. This definition must be specified using the following regular expression pattern: `[0-9]+(ms\|s\|m\|h\|d\|w\|y)` (ms = milliseconds, s= seconds,m = minutes, h = hours, d = days, w = weeks, y = years). The default value is `15d`.
+|retention|string|Defines the duration for which Prometheus retains data. This definition must be specified using the following regular expression pattern: `[0-9]+(ms\|s\|m\|h\|d\|w\|y)` (ms = milliseconds, s= seconds,m = minutes, h = hours, d = days, w = weeks, y = years). The default value is `24h`.
 
 |tolerations|[]v1.Toleration|Defines tolerations for the pods.