Update Security String to 2021-08-05

Bug: 191053489
Change-Id: Ieba9625ca0ccedf285209954f1e766b20455c32f
(cherry picked from commit f5139e3087ed265c79fdef47a4d0dd576a025379)
diff --git a/core/version_defaults.mk b/core/version_defaults.mk
index 13b85c0..f900f89 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 := 2021-07-05
+      PLATFORM_SECURITY_PATCH := 2021-08-05
 endif
 .KATI_READONLY := PLATFORM_SECURITY_PATCH