Revert "Update platform security string to 2018-11-05 on pi-dev & master"

This reverts commit dd737c09.

Reason for revert: Security String needs to be temporary reverted to cut a new 11-01 build 

Change-Id: I36e0f4de0c4158711fcc7a1f383129b8f3f889a1
(cherry picked from commit ad151b50f3b51022896ae674970a203b3f4c681e)