fixing Warning for acmd.py filter_files

To extract single evts or a list of evts from whatever file the
command 'acmd.py filter_files' is one of the recommended ways.
However, this command issues the following warning since a long
time:

WARNING Please stop using AtlCopyBSEvent.exe, and use AtlCopyBSEvent instead

This MR fixes that warning.


Former-commit-id: 16925630