use dynamic reference in link

docs/docs/domain.mdx

@@ -809,7 +809,7 @@ action_endpoint:
 ```
 **After selective domain for custom actions is enabled, domain will be sent only to
 those custom actions which have specifically stated that they need it.**
-Custom actions inheriting from rasa-sdk [FormValidationAction](https://rasa.com/docs/rasa/action-server/validation-action/#formvalidationaction-class)
+Custom actions inheriting from rasa-sdk [`FormValidationAction`](./action-server/validation-action.mdx#formvalidationaction-class)
 parent class are an exception to this rule as they will always have the domain sent to them.
 To specify if an action needs the domain add `{send_domain: true}` to custom action in the list
 of actions in `domain.yml`: