[Python][Packaging] Stop uploading nightly wheels to gemfury

[raulcd]

Describe the enhancement requested

Once we start uploading nightly wheels to the scientific python channel on anaconda:

• [Python] Uploading nightly wheels to the scientific python nightly channel #40216

we can drop uploading wheels to gemfury. We should also update any documentation about nightly wheels if any.

Component(s)

Packaging, Python

[jorisvandenbossche]

I think we should probably keep it for some time on both, and at least start with documenting the new index url as soon as possible.

(for example at least keep until 18.0 is released, when the stable docs will have the updated url)

[raulcd]

We don't seem to have updated the documentation on the new index URL, we should try update it for the next release.