CI: micromamba error

[twoertwein]

All CI runs seems to fail with: "Error: You are using a condarc file that is not named '.condarc'. This is currently not supported by micromamba, see mamba-org/mamba#1394"

https://github.com/pandas-dev/pandas/actions/runs/7209921420/job/19641945191?pr=56493

[pavelzw]

Sorry, this is from the latest release of setup-micromamba 😅 i'll replace this with a warning