Add returned default settings to `load_polldevs` docstring

[johannaengland]

Scope and purpose

This has been forgotten in #339.

Contributor Checklist

Every pull request should have this checklist filled out, no matter how small it is. More information about contributing to Zino can be found in the README.

• [ ] Added a changelog fragment for towncrier
  • only documentation change
• [ ] Added/amended tests for new/changed code
• [ ] Added/changed documentation
• [X] Linted/formatted the code with black, ruff and isort, easiest by using pre-commit
• [X] The first line of the commit message continues the sentence "If applied, this commit will ...", starts with a capital letter, does not end with punctuation and is 50 characters or less long. See https://cbea.ms/git-commit/
• [ ] If applicable: Created new issues if this PR does not fix the issue completely/there is further work to be done

[codecov[bot]]

Codecov Report

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

Project coverage is 98.30%. Comparing base (19ded46) to head (8b06822). Report is 55 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #345 +/- ## ========================================== + Coverage 98.20% 98.30% +0.10% ========================================== Files 64 64 Lines 7930 8005 +75 ========================================== + Hits 7787 7869 +82 + Misses 143 136 -7 ```

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[sonarcloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud