Update Security String to 2019-04-01
Bug: 124119313
(cherry picked from commit f9835d9f4d39c78ddf35899b058498f1908e906e)

Change-Id: I1a808f7c7ebaa29fcfae46f9225d5f385e9877dd
diff --git a/core/version_defaults.mk b/core/version_defaults.mk
index d386a52..e44746d 100644
--- a/core/version_defaults.mk
+++ b/core/version_defaults.mk
@@ -231,7 +231,7 @@
     #  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 := 2019-03-05
+      PLATFORM_SECURITY_PATCH := 2019-04-01
 endif
 
 ifndef PLATFORM_SECURITY_PATCH_TIMESTAMP