Remove workaround for arm subdirectories.

They no longer appear in APEXes, flattened or not.

This reverts https://r.android.com/1114092.

Test: art/build/apex/runtests.sh on aosp_x86_arm-userdebug,
  with and without OVERRIDE_TARGET_FLATTEN_APEX=true
Bug: 139046641
Change-Id: I692f9e991e321e73aaed1e1cce4038904d69d53d
1 file changed