Update x-pack/plugins/alerting/README.md

Co-authored-by: ymao1 <[email protected]>

x-pack/plugins/alerting/README.md

@@ -118,7 +118,7 @@ The following table describes the properties of the `options` object.
 |executor|This is where the code for the rule type lives. This is a function to be called when executing a rule on an interval basis. For full details, see the executor section below.|Function|
 |producer|The id of the application producing this rule type.|string|
 |minimumLicenseRequired|The value of a minimum license. Most of the rules are licensed as "basic".|string|
-|ruleTaskTimeout|The value could be used to override the task manager default timeout for a rule task. By default value will be set from alerting configuration "10m".|string|
+|ruleTaskTimeout|The length of time a rule can run before being cancelled due to timeout. By default, this value is "5m".|string|
 |useSavedObjectReferences.extractReferences|(Optional) When developing a rule type, you can choose to implement hooks for extracting saved object references from rule parameters. This hook will be invoked when a rule is created or updated. Implementing this hook is optional, but if an extract hook is implemented, an inject hook must also be implemented.|Function
 |useSavedObjectReferences.injectReferences|(Optional) When developing a rule type, you can choose to implement hooks for injecting saved object references into rule parameters. This hook will be invoked when a rule is retrieved (get or find). Implementing this hook is optional, but if an inject hook is implemented, an extract hook must also be implemented.|Function
 |isExportable|Whether the rule type is exportable from the Saved Objects Management UI.|boolean|