cmd.exe shell doesn't work with micromamba 1

[pavelzw]

#234 broke old micromamba versions, see #236

[pavelzw]

CC @JohanMabille @jjerphan

[pavelzw]

Also, could you introduce a comment in the code relevant code line referencing to #230 (comment) ?

Otherwise nobody will know why this change was made in a year from now

[pavelzw]

if you decide that you don't want to support micromamba 1 for setup-micromamba@v2, we should at least print out a meaningful error message that indicates this

[jjerphan]

I think that both major versions of micromamba and setup-micromamba must be tied, and that this should be documented.