Docs reference mamba.mamba_api but libmambapy should be used instead

[costrouc]

Close this issue if this is incorrect but in the docs https://github.com/mamba-org/mamba/blob/129920a304084a59bdfbe026b036185a83d94e40/docs/source/python_api.rst users are told to use from mamba import mamba_api. For me within version 0.21.2 this import fails. Could this be related to #1219. I've found that using import libmamba as mamba_api works to the same effect.

[wolfv]

Yeah, this needs an update, and a finish! The best reference for generic usage is the boa solver: https://github.com/mamba-org/boa/blob/master/boa/core/solver.py