FIX: list_coefficients -> coefficients_list

[mathause]

• [ ] Closes #xxx
• [ ] Tests added
• [ ] Passes isort . && black . && flake8
• [ ] Fully documented, including CHANGELOG.rst

The Expression class defines coefficients_list and not list_coefficients - or did I miss something?

https://github.com/MESMER-group/mesmer/blob/02169332a342275bf7e12db0dade60b5312ecc93/mesmer/mesmer_x/train_utils_mesmerx.py#L192

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.

Project coverage is 51.63%. Comparing base (9b0b76b) to head (8963776). Report is 60 commits behind head on main.

Files	Patch %	Lines
mesmer/mesmer_x/train_l_distrib_mesmerx.py	0.00%	2 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #469 +/- ## =========================================== - Coverage 87.90% 51.63% -36.28% =========================================== Files 40 50 +10 Lines 1745 3238 +1493 =========================================== + Hits 1534 1672 +138 - Misses 211 1566 +1355 ``` | [Flag](https://app.codecov.io/gh/MESMER-group/mesmer/pull/469/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=MESMER-group) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/MESMER-group/mesmer/pull/469/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=MESMER-group) | `51.63% <0.00%> (-36.28%)` | :arrow_down: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=MESMER-group#carryforward-flags-in-the-pull-request-comment) to find out more.

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[mathause]

Thanks