Update Security String to 2021-04-05

Bug: 179275902
Change-Id: Iac6942fe3ffb72e2ae1d1c4ea653d1bf9f4e89e9
(cherry picked from commit 1f4aeb1430efaafbb3e0b5f34fdc624deb28a2f9)
diff --git a/core/version_defaults.mk b/core/version_defaults.mk
index 9c7ac2c..e83b8b0 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 := 2021-03-05
+      PLATFORM_SECURITY_PATCH := 2021-04-05
 endif
 .KATI_READONLY := PLATFORM_SECURITY_PATCH