Fix conda-forge CI November 2025

[traversaro]

This PR fixes the conda-forge CI:

• For macOS/Linux and gh-pages CI, this is fixed by removing the old workaround for defauls packages are always installed regardless of the channels option conda-incubator/setup-miniconda#186 with the appropriate solution of setting the conda-remove-defaults: true parameter
• For Windows, I skipped the Python tests as a workaround for CI errors on windows #992 . It would be good to eventually fix that (so I would keep the issue CI errors on windows #992 open) but Python tests are passing fine in the feedstock, so I do not think this is particularly problematic, while it is much more problematic to have the CI red for all PRs

[traversaro]

CI is happy, @S-Dafarra @GiulioRomualdi can we quickly merge to unblock the other PRs? Thanks!

fyi @xela-95

[traversaro]

Thanks a lot @GiulioRomualdi !