Making sys.boot.reason.last restricted

sys.boot.reason.last needs to be readable by SysUI to correctly display the reason why authentication is required to unlock the phone.

Bug: 299327097
Test: presubmit
Change-Id: I9f83ade92858056609bc665ecb6ce9b93eb051e4
diff --git a/private/bootstat.te b/private/bootstat.te
index 016292e..99d8c6d 100644
--- a/private/bootstat.te
+++ b/private/bootstat.te
@@ -17,6 +17,7 @@
   -dumpstate
   userdebug_or_eng(`-incidentd')
   -init
+  -platform_app
   -recovery
   -shell
   -system_server