Add documentation on usage of net-utils-connectivity-apks am: 514f40b0c3 am: c851185244

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Connectivity/+/3220095

Change-Id: I3ff2f86542f0861b0d4e8a8ea8cad870e2153995
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>