Fix: Correct broken API link in execution-history-cleaner.md

Changed /api/rundeck-api.md#executions to /api/index.md#executions.

The correct API documentation file is index.md, not rundeck-api.md.
Fixes broken link warning found by dev server.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: fdevans

docs/manual/projects/execution-history-cleaner.md

@@ -385,4 +385,4 @@ curl -X PUT \
 
 - [Project Settings](/manual/project-settings.md) - General project configuration
 - [Activity](/manual/08-activity.md) - View execution history
-- [Executions API](/api/rundeck-api.md#executions) - Programmatic execution management
+- [Executions API](/api/index.md#executions) - Programmatic execution management