Update Security String to 2021-09-01

Bug: 192405736
Change-Id: Ie53aed2831d96e9806657e9b8472805f36d54419
Merged-In: Icea699ec7f82744ff0a6dca90068b2737129778a
diff --git a/core/version_defaults.mk b/core/version_defaults.mk
index b06dd18..da69bb0 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 := 2021-08-01
+      PLATFORM_SECURITY_PATCH := 2021-09-01
 endif
 
 ifndef PLATFORM_BASE_OS