[CI] windows: micromamba pip installation from zip fails

[orbeckst]

The following error is now failing Windows CI runners (e.g. https://github.com/alchemistry/alchemlyb/actions/runs/11134663073/job/30943263819?pr=417 )

Installing pip packages: alchemtest @ https://github.com/alchemistry/alchemtest/archive/master.zip
  '"C:\Users\runneradmin\micromamba\condabin\micromamba"' is not recognized as an internal or external command,
  operable program or batch file.
  critical libmamba pip failed to install packages
  Error: The process 'C:\Users\runneradmin\micromamba-bin\micromamba.exe' failed with exit code 1