Update Security String to 2020-12-05 am: 29d48ffac5 am: 9841d4bcfa am: b487704e79 am: 675376fe18

Original change: https://googleplex-android-review.googlesource.com/c/platform/build/+/12819559

Change-Id: I6a81f79494b39664aaeef5f57b78ad31749bd435