[automerger skipped] Update Security String to 2021-10-01 am: 6ccb50dd3a am: 3644c700aa -s ours

am skip reason: Merged-In I4a0cd58b18214b77302ae7ed81c189f4549dc41d with SHA-1 91cbb67645 is already in history

Original change: https://googleplex-android-review.googlesource.com/c/platform/build/+/15564069

Change-Id: Ib69109d27d8c3dc95fc8175453a189a83b20303c