Add comment on ssh kill command

ci/scripts/driver.sh

@@ -108,6 +108,7 @@ for pr in ${pr_list}; do
            echo -e "${pstree_out}" | grep -Pow "(?<=\()[0-9]+(?=\))" | xargs kill
         fi
       else
+        # Check if the driver is still running on the head node; if so, kill it and all child processes
         ssh "${driver_HOST}" "if ps -p ${driver_PID} 2>&1; then pstree -A -p \"${driver_PID}\" | grep -Eow \"[0-9]+\" | xargs kill; fi"
       fi
       {