Please update default version of mamba in setup-miniconda v3

[valeriupredoi]

Hi folks, first off - and I always start on this note when I open an issue here - many thanks yet again for your great work! 🍻
Now, we started seeing transitory failures, eg failed test here, maybe about 5% of times - and this has been going on for a wee while now (about a month or so). U realized the default version of mamba is rather ye olde (1.5 vs latest 2.0+), so I tested with mamba-version: "2.0.5" in a test branch, and ran quite a few test iterations - no flakiness at all and 100% pass rate, so it'd be a good idea if you could update the base default version of mamba - let me know if you'd accept a PR from me on that, or if it'd easier for you to do it! Cheers muchly!

[jaimergp]

Yea, this can happen once conda-forge/miniforge#715 lands.

[valeriupredoi]

@jaimergp brilliant, many thanks! 🍻 Shall be waiting in the queue then 😁