ElasticNetCVLearner: Fix parameter alphas

[janezd]

Issue

ElasticNetCVLearner requires int or an array, and no longer accepts None.

Description of changes

Set it to the default value, 100. This duplicates the value of n_alpha, which we need to keep for compatibility

We have a problem with scikit versions and should probably require 1.7. We currently require 1.5

• 1.5 (from 2024) does not accept an int argument for alpha; it requires a list or None (default, effectively sets it to 100).
• 1.7 (2025) deprecates allows int and deprecates None; it defaults to 100.
• 1.9 (2026) no longer accepts None.

There is no common argument type for 1.5 and 1.9. If we omit the argument to use the default, we have a problem with signature.

The easiest solution is to require Scikit 1.7

Includes

• Code changes

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.03%. Comparing base (441070e) to head (3fbfc16).
⚠️ Report is 3 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #7294   +/-   ##
=======================================
  Coverage   89.03%   89.03%           
=======================================
  Files         336      336           
  Lines       74433    74427    -6     
=======================================
- Hits        66273    66268    -5     
+ Misses       8160     8159    -1     

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