Fix envvar name in snapshot CI

[glatterf42]

#281 renamed the environment variable for the python version of our snapshot CI test from python to python-version. The uv action could not find env.python and thus saw no input for python-version, which it needs to create a venv. And without a venv, we get the error we see in today's snapshot CI test.

This PR adjust the name of the environment variable used for the uv action.

How to review

• Read the diff and note that the variable name used now is correct.

PR checklist

• Continuous integration checks all ✅
• Add or expand tests; coverage checks both ✅
• [ ] Add, expand, or update documentation. Just CI.
• [ ] Update doc/whatsnew. Just CI.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 76.7%. Comparing base (3fe0467) to head (f436bfd).
Report is 1 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main    #283   +/-   ##
=====================================
  Coverage   76.7%   76.7%           
=====================================
  Files        211     211           
  Lines      16108   16108           
=====================================
  Hits       12363   12363           
  Misses      3745    3745           

[khaeru]

Good catch, thanks!