KeyError: 'release_arena' when powering off a box or powering on a box, the box power subcommand does not work

The box power subcommand seems to always fail with a KeyError.
```
HackTheBox> box power off
[*] Powering off Interface...
KeyError: 'release_arena'
HackTheBox> 
```
I don't know exactly why but there might be changes upstream on the release_arena keyword of the HTBClient library.

If there is any way I can PR or help to fix this issue, feel free to let me know.