How to disable index copying

Hello,

When I run `cbmigrate` with `--copy-indexes false` argument indexes are copied anyway. Default value of this flag is `true` so if I don't pass it, indexes will copy again.
What is the proper way to disable index copying?
Source cluster is MongoDB Atlas.

```
$ ./cbmigrate --version
Version: 1.0.2
$ ./cbmigrate ... --copy-indexes false --debug
...
INFO data migration completed
INFO index migration started
DEBUG index idx_1 created successfully
DEBUG index idx_2 created successfully
...
DEBUG index idx_n created successfully
DEBUG Indexes deferred are now building in background
INFO index migration completed
```