fix spacing in env.yaml to allow CI build

[Mikejmnez]

This PR fixes the CI build errors with micromambav2 that fail to build the appropriate environment. The specific errors are:

critical libmamba Error parsing MatchSpec "xesmf[version='>',build=0.6.3]": Error setting attribute "version" to value ">": Error parsing version "". Empty version."

The issue is that micromamba2 cannot parse the empty space in the yml file next to the packages. And so it attempts to find a matching version == '>'.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.62%. Comparing base (536b9fb) to head (f54d649).
Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #453   +/-   ##
=======================================
  Coverage   95.62%   95.62%           
=======================================
  Files           9        9           
  Lines        5163     5163           
  Branches     1008     1008           
=======================================
  Hits         4937     4937           
  Misses        133      133           
  Partials       93       93           

Flag	Coverage Δ
unittests	95.62% <ø> (ø)

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[ThomasHaine]

Looks great to me!