Add returned default settings to load_polldevs docstring

[johannaengland]

Scope and purpose

This has been forgotten in #339.

Contributor Checklist

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• Added a changelog fragment for towncrier
  • only documentation change
• Added/amended tests for new/changed code
• Added/changed documentation
• Linted/formatted the code with black, ruff and isort, easiest by using pre-commit
• 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]

Codecov Report

All modified and coverable lines are covered by tests ✅

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

Additional details and impacted files

@@            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]

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