fix: creation of virtual machine instances

[domodwyer]

Hi!

First off, thanks for the work to make this collection! I've found it really helpful.

I was struggling to provision a VM though - it looks like it's a simple validation failure and it works with the attached patch.

% incus version
Client version: 6.7
Server version: 6.0.2

---

• fix: creation of virtual machine instances (4267852)

  The incus_instance task would only allow "container" and "vm" to be passed as the instance type, but using "vm" would rest in a server error:

    Unexpected instance type "vm"

  The argument sent by the CLI is "virtual-machine":

    {
            "architecture": "",
            "config": {},
            "devices": {},
            "ephemeral": false,
            "profiles": null,
            "stateful": false,
            "description": "",
            "name": "bananas",
            "source": {
                    "type": "image",
                    "certificate": "",
                    "alias": "debian/bookworm/cloud",
                    "server": "https://images.linuxcontainers.org",
                    "protocol": "simplestreams",
                    "mode": "pull",
                    "allow_inconsistent": false
            },
            "instance_type": "",
      -->   "type": "virtual-machine",   <--
            "start": true
    }

  This commit fixes the validation logic to allow the correct VM instance type to be sent.

[kmpm]

Great find. Could you please correct the documentation in the same file as well?