Use a var for doc URLs instead of hardcoding

docs/upgrade-notes.asciidoc

@@ -71,16 +71,16 @@ Deprecated endpoints will fail with a 404 status code starting from version 9.0.
 Update your implementations to use the new endpoints:
 
 * **For bulk creation of rules:**
-   - Use `POST /api/detection_engine/rules/_import` (link:https://www.elastic.co/docs/api/doc/kibana/v8/operation/operation-importrules[API documentation]) to create multiple rules along with their associated entities (for example, exceptions and action connectors).
-   - Alternatively, create rules individually using `POST /api/detection_engine/rules` (link:https://www.elastic.co/docs/api/doc/kibana/v8/operation/operation-createrule[API documentation]).
+   - Use `POST /api/detection_engine/rules/_import` (link:{api-kibana}/operation/operation-importrules[API documentation]) to create multiple rules along with their associated entities (for example, exceptions and action connectors).
+   - Alternatively, create rules individually using `POST /api/detection_engine/rules` (link:{api-kibana}/operation/operation-createrule[API documentation]).
 
 * **For bulk updates of rules:**
-   - Use `POST /api/detection_engine/rules/_bulk_action` (link:https://www.elastic.co/docs/api/doc/kibana/v8/operation/operation-performrulesbulkaction[API documentation]) to update fields in multiple rules simultaneously.
-   - Alternatively, update rules individually using `PUT /api/detection_engine/rules` (link:https://www.elastic.co/docs/api/doc/kibana/v8/operation/operation-updaterule[API documentation]).
+   - Use `POST /api/detection_engine/rules/_bulk_action` (link:{api-kibana}/operation/operation-performrulesbulkaction[API documentation]) to update fields in multiple rules simultaneously.
+   - Alternatively, update rules individually using `PUT /api/detection_engine/rules` (link:{api-kibana}/operation/operation-updaterule[API documentation]).
 
 * **For bulk deletion of rules:**
-   - Use `POST /api/detection_engine/rules/_bulk_action` (link:https://www.elastic.co/docs/api/doc/kibana/v8/operation/operation-performrulesbulkaction[API documentation]) to delete multiple rules by IDs or query.
-   - Alternatively, delete rules individually using `DELETE /api/detection_engine/rules` (link:https://www.elastic.co/docs/api/doc/kibana/v8/operation/operation-deleterule[API documentation]).
+   - Use `POST /api/detection_engine/rules/_bulk_action` (link:{api-kibana}/operation/operation-performrulesbulkaction[API documentation]) to delete multiple rules by IDs or query.
+   - Alternatively, delete rules individually using `DELETE /api/detection_engine/rules` (link:{api-kibana}/operation/operation-deleterule[API documentation]).
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