Update options validation for 7.x

#### Community Note

Please vote on this issue by adding a 👍 [reaction](https://blog.github.com/2016-03-10-add-reactions-to-pull-requests-issues-and-comments/) to the original issue to help the community and maintainers prioritize this request.
Please do not leave "+1" or "me too" comments, they generate extra noise for issue followers and do not help prioritize the request.
If you are interested in working on this issue or have submitted a pull request, please leave a comment.

#### Description

In VBox 7.1.x the graphics controller option gained `QemuRamFB` as a valid choice, but packer says it's not a valid value.

#### Use Case(s)

`QemuRamFB` is apparently required to successfully boot arm64 machines using VBox 7.2+ under macOS.

#### Potential configuration

```
gfx_controller = "QemuRamFB"
```

#### Potential References

https://docs.oracle.com/en/virtualization/virtualbox/7.1/user/vboxmanage.html#vboxmanage-cmd-overview__synopsis-vboxmanage-modifyvm-general