[automerger skipped] Update Security String to 2021-09-01 am: 639164b2 am:...

[automerger skipped] Update Security String to 2021-09-01 am: 639164b2 am: 996d1d3a am: abecfaa9 am: 28bb26ce -s ours

am skip reason: Merged-In Icea699ec7f82744ff0a6dca90068b2737129778a with SHA-1 cfd4896d is already in history

Original change: https://googleplex-android-review.googlesource.com/c/platform/build/+/15123745

Change-Id: I0edba4615416cd7a867ca367318e3a9db76dcc60