docs: update FAQ with info about `allow-scale-down-on-custom-controll…

…er-owned-pods` flag

Signed-off-by: vadasambar <surajrbanakar@gmail.com>

cluster-autoscaler/FAQ.md

@@ -791,6 +791,7 @@ The following startup parameters are supported for cluster autoscaler:
 | `feature-gates` | A set of key=value pairs that describe feature gates for alpha/experimental features. | ""
 | `cordon-node-before-terminating` | Should CA cordon nodes before terminating during downscale process | false
 | `record-duplicated-events` | Enable the autoscaler to print duplicated events within a 5 minute window. | false
+| `allow-scale-down-on-custom-controller-owned-pods` | Don't block node scale-down if a pod owned by a custom controller is running on the node. | false
 
 # Troubleshooting: