Update Security String to 2020-10-01

Bug: 163542576
Change-Id: I4973247ab66704c16446c47c6fd830a21ea2504f
(cherry picked from commit da6e4c1964d01e71cd173267fda01bacdd25b5d4)
diff --git a/core/version_defaults.mk b/core/version_defaults.mk
index 71334d0..e867ebb 100644
--- a/core/version_defaults.mk
+++ b/core/version_defaults.mk
@@ -240,7 +240,7 @@
     #  It must be of the form "YYYY-MM-DD" on production devices.
     #  It must match one of the Android Security Patch Level strings of the Public Security Bulletins.
     #  If there is no $PLATFORM_SECURITY_PATCH set, keep it empty.
-      PLATFORM_SECURITY_PATCH := 2020-09-05
+      PLATFORM_SECURITY_PATCH := 2020-10-01
 endif
 .KATI_READONLY := PLATFORM_SECURITY_PATCH