Pin Miniforge

[smithdc1]

While we're waiting for a fix to asv to be compatabile with recent versions of conda let's try and pin to a conda version which works.

[smithdc1]

@sarahboyce what do you think?

[sarahboyce]

Let's do it 👍

[sarahboyce]

@smithdc1 do you know if we need to do a similar change in django's benchmark GitHub action?
This doesn't look like it completed properly: https://github.com/django/django/actions/runs/9188334939/job/25267947914?pr=18187 🤔

[smithdc1]

Yes. That seems to make sense. I think that's the best option for now.