Refactor bias_variance_decomposition test.

[fkdosilovic]

Description

Refactors two tests in evaluate/tests/test_bias_variance_decomp.py (change base_estimator to estimator). This fixes two failing unit tests.

Related issues or pull requests

None.

Pull Request Checklist

• [x] Added a note about the modification or contribution to the ./docs/sources/CHANGELOG.md file (if applicable)
• [x] Added appropriate unit test functions in the ./mlxtend/*/tests directories (if applicable)
• [x] Modify documentation in the corresponding Jupyter Notebook under mlxtend/docs/sources/ (if applicable)
• [x] Ran PYTHONPATH='.' pytest ./mlxtend -sv and make sure that all unit tests pass (for small modifications, it might be sufficient to only run the specific test file, e.g., PYTHONPATH='.' pytest ./mlxtend/classifier/tests/test_stacking_cv_classifier.py -sv)
• [x] Checked for style issues by running flake8 ./mlxtend

[rasbt]

Arg, good catch, thanks!

[rasbt]

Thanks a lot, I somehow missed this and will check it out!

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 78.32%. Comparing base (506a4d5) to head (2d61b28).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1081   +/-   ##
=======================================
  Coverage   78.32%   78.32%           
=======================================
  Files         196      196           
  Lines       11157    11157           
  Branches     1404     1404           
=======================================
  Hits         8739     8739           
  Misses       2200     2200           
  Partials      218      218           

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[rasbt]

Thanks for updating this, I appreciate it!