qa/btrfs/test_rmdir_async_snap: remove binary file

On a quick look at the source code, I noticed this binary file, which
looks like was committed by mistake.

Signed-off-by: Cleber Rosa <crosa@redhat.com>

diff --git a/qa/btrfs/test_rmdir_async_snap b/qa/btrfs/test_rmdir_async_snap
deleted file mode 100755 (executable)
index f128a6b..0000000
Binary files a/qa/btrfs/test_rmdir_async_snap and /dev/null differ