Allow system_server to set arm64 memtag property

Bug: 262763327
Bug: 244290023
Test: atest MtePolicyTest on user build
Test: manually with TestDPC
Change-Id: If1ed257fede6fa424604eed9775eb3a3b8365afe
diff --git a/private/property.te b/private/property.te
index cac04d3..dee6369 100644
--- a/private/property.te
+++ b/private/property.te
@@ -432,6 +432,7 @@
   -init
   -shell
   -system_app
+  -system_server
   -mtectrl
 } {
   arm64_memtag_prop