Update Security String to 2021-03-05

Bug: 177091143
Change-Id: I6d6542306c51ac1682f02cbce6701688d2bdbea2
(cherry picked from commit 9c4665257c947d57783d6593dbd33e4c686419fc)
diff --git a/core/version_defaults.mk b/core/version_defaults.mk
index e610490..9c7ac2c 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 := 2021-02-05
+      PLATFORM_SECURITY_PATCH := 2021-03-05
 endif
 .KATI_READONLY := PLATFORM_SECURITY_PATCH