Remove artApex parameter from ApexBundleFactory

Since coverage support was added to bootclasspath_fragment in
https://r.android.com/1684807 and bootclasspath_fragments were
integrated into the ART APEX it is no longer necessary to treat ART
APEXes differently to other APEXes.

Change https://r.android.com/1684807 added coverage support, follow
up changes integrated

Bug: 177892522
Test: m droid
      m EMMA_INSTRUMENT=true EMMA_INSTRUMENT_FRAMEWORK=true
Change-Id: I4800a003c7459c4686607e16f4c5bde0be105f16