docs(resource_actions): specify when mergeBuiltinActions was introduc…

…ed (argoproj#20917)

The feature was made available in 2.13.0 onwards.

Signed-off-by: Nicholas Morey <nicholas@morey.tech>
Signed-off-by: Adrian Aneci <aneci@adobe.com>

docs/operator-manual/resource_actions.md

@@ -80,7 +80,7 @@ The `discovery.lua` script must return a table where the key name represents the
 
 Each action name must be represented in the list of `definitions` with an accompanying `action.lua` script to control the resource modifications. The `obj` is a global variable which contains the resource. Each action script returns an optionally modified version of the resource. In this example, we are simply setting `.spec.suspend` to either `true` or `false`.
 
-By default, defining a resource action customization will override any built-in action for this resource kind. If you want to retain the built-in actions, you can set the `mergeBuiltinActions` key to `true`. Your custom actions will have precedence over the built-in actions.
+By default, defining a resource action customization will override any built-in action for this resource kind. As of Argo CD version 2.13.0, if you want to retain the built-in actions, you can set the `mergeBuiltinActions` key to `true`. Your custom actions will have precedence over the built-in actions.
 ```yaml        
 resource.customizations.actions.argoproj.io_Rollout: |
   mergeBuiltinActions: true
@@ -202,4 +202,4 @@ resource.customizations.actions.ConfigMap: |
       result[1] = impactedResource1
       result[2] = impactedResource2
       return result		  
-```
+```