Fix the ART APEX flavor auto-detection logic in `art_apex_test.py`.

The "release" flavor is no longer explicitly part of the Release ART
APEX file name; adjust the auto-detection logic in script
`build/apex/art_apex_test.py` accordingly.

Test: art/build/apex/runtests.sh
Change-Id: I6ededa600acab5365ade7011f824ae38a41497d1
1 file changed