libbacktrace: Delete test data that will never be used.

We've mirrored libbacktrace so that we can provide stub implementations
of some of the functions. We'll never use this test data so remove so
that clients don't need to download it.

BUG=None
TEST=None

Change-Id: I912854033bc3e74e321aed30de6d86372ca2431f
Cr-Mirrored-From: https://chromium.googlesource.com/aosp/platform/system/core
Cr-Mirrored-Commit: 087796c31c8726b60c7471eaf0621da6100ef092
21 files changed