Fix some CI errors

[bnavigator]

Fixes:

• Ubuntu dropped the libopenblas-base "transition" package
• Mambaforge is deprecated
• Windows mamba commands silently fail
• macOS conda MKL error during pytest collection

[slivingston]

Windows mamba commands silently fail

@bnavigator I looked in the recent CI logs, but I did not find evidence about the mamba command failing silently. Can you show me?

Also, I am motivated to ask because a mamba command is used similarly in python-control CI jobs: https://github.com/python-control/python-control/blob/a2c3b4c8db5558181357d2762e2285ae2ea01dc5/.github/workflows/os-blas-test-matrix.yml#L312

[roryyorke]

looks good, thanks @bnavigator .

[bnavigator]

Yes, I noticed that it works on the python-control jobs. But it failed here: https://github.com/python-control/Slycot/actions/runs/12467342357/job/34797033932#step:7:27 The commands just printed out the current windows version (!?)

See conda-incubator/setup-miniconda#371

[bnavigator]

Oh, it also does not work on the python-control jobs: https://github.com/python-control/python-control/actions/runs/12468173712/job/34799709028#step:7:27
The installs for slycot do not happen. Notice how the tests are automatically skipped by pytest: https://github.com/python-control/python-control/actions/runs/12468173712/job/34799709028#step:8:165