COLORTERM not imported into Ubuntu instance

Even though the `AcceptEnv` setting has been added, the variable is not accepted, even after a restart of the instance (which shouldn't be necessary anyways):

```console
$ lima sudo grep AcceptEnv /etc/ssh/sshd_config
AcceptEnv COLORTERM LANG LC_*
$ COLORTERM=truecolor lima env | grep COLOR
```
@afbjorklund Am I missing something about how this should work, or has it been broken since the initial implementation?

Ref #2202