[RUN-4429] Document child process kill limitation

Author: jayas006

docs/manual/jobs/index.md

@@ -210,4 +210,8 @@ When prompted "Really kill this job?" Click the "Yes" button.
 
 The Job will terminate with a "Killed" completion status.
 
+> **Note:** Killing a job stops the job and the main process Rundeck controls.
+> Child processes spawned by the job may not be killed.
+> This is a known platform limitation and is not guaranteed.
+
 ![Job definition](/assets/img/fig0319-d.png)