Update Security String to 2021-10-01 am: 6ccb50dd3a

Original change: https://googleplex-android-review.googlesource.com/c/platform/build/+/15564069

Change-Id: Ic204e600b0b34ad39a50383f17fb74da668c0c9c
diff --git a/core/version_defaults.mk b/core/version_defaults.mk
index 4bc4498..4a00f44 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 := 2021-10-01
 endif
 .KATI_READONLY := PLATFORM_SECURITY_PATCH