BLD: Revert micromamba version to v2

[mtsokol]

This PR reverts CI change introduced in #799.

[mtsokol]

I think we should merge it once windows job passes, so when mamba-org/setup-micromamba#227 is fixed. WDYT?

[hameerabbasi]

I think we should merge it once windows job passes, so when mamba-org/setup-micromamba#227 is fixed. WDYT?

SGTM, can't merge it until CI passes anyway. So my recommendation would be to re-run the CI and then merge after a fix.

[codspeed-hq]

CodSpeed Performance Report

Merging #805 will degrade performances by 34.38%

_{Comparing micromamba-v2 (fda977f) with main (c0b2b45)}

Summary

⚡ 1 improvements
❌ 1 regressions
✅ 338 untouched benchmarks

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Benchmark	main	micromamba-v2	Change
❌	test_index_slice[side=100-rank=2-format='gcxs']	2.4 ms	3.6 ms	-34.38%
⚡	test_elemwise[f=<built-in function gt>-backend='Finch'-side=1000]	62 ms	1.5 ms	×42

[mtsokol]

I think we can merge it - the bug was solved in mamba (failing job is unrelated I think)

[hameerabbasi]

Thanks, @mtsokol!