Update Security String to 2021-10-01

Bug: 193547118
Change-Id: I84157c79f00951e9600a2924e6c6fbc497a5e1ef
Merged-In: I36d8511d8ab1556af5c278c8d65d7c3ee6f1878d
diff --git a/core/version_defaults.mk b/core/version_defaults.mk
index da69bb0..cffc738 100644
--- a/core/version_defaults.mk
+++ b/core/version_defaults.mk
@@ -181,7 +181,7 @@
     #  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 := 2021-09-01
+      PLATFORM_SECURITY_PATCH := 2021-10-01
 endif
 
 ifndef PLATFORM_BASE_OS