Update Security String to 2021-10-05

Bug: 193547118
Change-Id: I4a0cd58b18214b77302ae7ed81c189f4549dc41d
(cherry picked from commit 91cbb6764503275e87f6171f0308aebd76f4dcb9)
diff --git a/core/version_defaults.mk b/core/version_defaults.mk
index 663579a..85f63c9 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 := 2021-09-05
+      PLATFORM_SECURITY_PATCH := 2021-10-05
 endif
 .KATI_READONLY := PLATFORM_SECURITY_PATCH