kernel.te: drop allow kernel untrusted_app:fd use;

auditallow says it's not used.

Bug: 25331459
Change-Id: Ic414efcd0a3be6d744ab66382c20f0ea4c9ea116

kernel.te

@@ -42,10 +42,7 @@ allow kernel self:security setcheckreqprot;
 
 # MTP sync (b/15835289)
 # kernel thread "loop0", used by the loop block device, for ASECs (b/17158723)
-allow kernel { priv_app untrusted_app }:fd use;
-# privileged apps have moved to the priv_app domain. Determine
-# if this permission is still needed. b/25331459
-auditallow kernel untrusted_app:fd use;
+allow kernel priv_app:fd use;
 allow kernel sdcard_type:file { read write };
 
 # Allow the kernel to read OBB files from app directories. (b/17428116)