webview_zygote: allow listing dirs in /system

For consistency with zygote, allow webview_zygote to list directories
in /system.

Test: Boot Taimen. Verify webiew_zygote denials during boot.
Bug: 70857705
Change-Id: I27eb18c377a5240d7430abf301c1c3af61704d59

private/webview_zygote.te

@@ -54,6 +54,9 @@ selinux_check_context(webview_zygote)
 # Check SELinux permissions.
 selinux_check_access(webview_zygote)
 
+# Directory listing in /system.
+allow zygote system_file:dir r_dir_perms;
+
 #####
 ##### Neverallow
 #####