Update Security String to 2021-02-01

Bug: 175313938

Change-Id: I6d6c4a8d4f3e80c40754670ae60718aa42c3265d
Merged-In: I6a1139d288c24a11289fc53c9022fd6d70acd8e6

core/version_defaults.mk

@@ -181,7 +181,7 @@ ifndef PLATFORM_SECURITY_PATCH
     #  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 := 2021-01-01
+      PLATFORM_SECURITY_PATCH := 2021-02-01
 endif
 
 ifndef PLATFORM_BASE_OS