Updating docs to use the `--tools-file` flag over the now deprecated
`--tools_file`.
The new flag was added as of `v0.3.0` in #384
This change reduces confusion as current usage in docs results in
following message on startup of Toolbox server:
```sh
Flag --tools_file has been deprecated, please use --tools-file instead
```
Fixes#514
---------
Co-authored-by: Yuan <45984206+Yuan325@users.noreply.github.com>
