pin micromamba version to latest

[atravitz]

as discussed in #1193

Checklist

• Added a news entry

Developers certificate of origin

• I certify that this contribution is covered by the MIT License here and the Developer Certificate of Origin at https://developercertificate.org/.

[mikemhenry]

Is this different from the default? If it is the default, do we just want to remove it?

[atravitz]

Is this different from the default? If it is the default, do we just want to remove it?

I was 50/50 on this - I know in the past we've had confusion where a newer version of micromamba was pulling in a different package for whatever reason, so I thought it would be helpful to be explicit here. Happy to remove completely if you feel otherwise.

[github-actions]

No API break detected ✅

[mikemhenry]

we print out the micromamba version

so that will help with debugging, this will also be nice since then we will get updates without having to remember to check for them

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.20%. Comparing base (9974040) to head (d0c1b87).
⚠️ Report is 126 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1348      +/-   ##
==========================================
- Coverage   95.11%   93.20%   -1.92%     
==========================================
  Files         165      165              
  Lines       12389    12389              
==========================================
- Hits        11784    11547     -237     
- Misses        605      842     +237     

Flag	Coverage Δ
fast-tests	93.20% <ø> (?)
slow-tests	?

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