Rework install instructions to move away from conda

[bsipocz]

Anaconda has changed its ToC, and therefore I strongly feel it would be wise to rework the install instructions either to use miniforge instead, or pixi, or good old python environments instead of conda and thus risk pulling in dependencies from the default channel (we won't be pulling in such a dependency with the workshop materials, but the users may do, and thus can be subject to the licence fees), etc.

I add this as high priority as this cleanup should happen before the next workshop.