Remove unavailable cloud vendors: auroracompute; InternetSolutions; dimension data

## Summary

Adding support for all your cloud vendors and came across broken domains for:
- https://libcloud.readthedocs.io/en/stable/compute/drivers/auroracompute.html (which has a domain that is for sale)
- https://libcloud.readthedocs.io/en/stable/compute/drivers/internetsolutions.html (http://www.is.co.za site is down)
- https://libcloud.readthedocs.io/en/stable/compute/drivers/dimensiondata.html (redirects to ntt now which has two other vendors on libcloud already… I assume this company was bought by NTT)

Might be worth removing these vendors. (might update this issue with PRs and any other vendors that have disappeared)

Start with the three referenced driver documentation pages for auroracompute, internetsolutions, and dimensiondata, then locate their corresponding implementations and repository references. Confirm the vendors are unavailable and check any related tests or documentation; the work is done when obsolete support and references are removed consistently.

Written by the indexing model from the issue text.