Ruby 4 compatibility

I have updated to Ruby 4 and the droplet_kit gem version has been downgraded.

```
Because droplet_kit >= 3.20.0 depends on faraday-retry ~> 2.2.0
and faraday-retry >= 2.0.0, < 2.4.0 depends on Ruby >= 2.6, < 4,
droplet_kit >= 3.20.0 requires Ruby >= 2.6, < 4.
So, because Gemfile depends on droplet_kit ~> 3.22
and current Ruby version is = 4.0.1,
version solving has failed.
```

Please update dependency on faraday-retry.