fix mythic connector with unwaited coroutine

[Matixx22]

Mythic connector File Handler issue

Before the fix I was getting this error running the mythic connector:

/venv/lib/python3.13/site-packages/cli/mythic_connector/handlers.py:133: RuntimeWarning: coroutine 'FileHandler.handle_file.<locals>.upload_to_nemesis' was never awaited
  download_callback(path)
RuntimeWarning: Enable tracemalloc to get the object allocation traceback

The fix introduces the change in the Mythic connector's FileHandler.download_file method. The download_callback (upload_to_nemesis) is an async function but was being called without await, causing downloaded files to never be uploaded to Nemesis. Adding await to the callback call resolves the issue.

If you encounter this issue locally try to rebuild the local docker nemesis-cli image with this change.

[leechristensen]

Thank you!