Drop levelFrom=none from untrusted_app entry.

In the absence of any levelFrom= specifier, the default is none,
so this is unnecessary and conspicuous in contrast to all other
entries.  It came from switching our default of levelFrom=app
to levelFrom=none in AOSP rather than just dropping it.

Change-Id: Ia2f8c72200318ef66a1b6d6b6c117f8848441d7f
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>