Allow ephemeral_app to execute system_file.

(cherrypicked from commit f2afca7c)

Bug: 109653662
Test: Build policy.
Change-Id: I6c71a8bc24d7a144b801d16f1bcad31fb8f2aba5
Merged-In: I6c71a8bc24d7a144b801d16f1bcad31fb8f2aba5

public/app.te

@@ -87,7 +87,7 @@ allow appdomain oemfs:file rx_file_perms;
 # Execute the shell or other system executables.
 allow { appdomain -ephemeral_app -untrusted_v2_app } shell_exec:file rx_file_perms;
 allow { appdomain -ephemeral_app -untrusted_v2_app } toolbox_exec:file rx_file_perms;
-allow { appdomain -ephemeral_app -untrusted_v2_app } system_file:file x_file_perms;
+allow { appdomain -untrusted_v2_app } system_file:file x_file_perms;
 not_full_treble(`allow { appdomain -ephemeral_app -untrusted_v2_app } vendor_file:file x_file_perms;')
 
 # Renderscript needs the ability to read directories on /system