Fix some docstrings

[KJhellico]

Proposed change

Fix some docstrings (in HolidayBase::pop_named and _ThaiLunisolar).

Type of change

• [ ] New country/market holidays support (thank you!)
• [ ] Supported country/market holidays update (calendar discrepancy fix, localization)
• [ ] Existing code/documentation/test/process quality improvement (best practice, cleanup, refactoring, optimization)
• [ ] Dependency update (version deprecation/pin/upgrade)
• [x] Bugfix (non-breaking change which fixes an issue)
• [ ] Breaking change (a code change causing existing functionality to break)
• [ ] New feature (new python-holidays functionality in general)

Checklist

• [x] I've followed the contributing guidelines
• [x] I've run make pre-commit, it didn't generate any changes
• [x] I've run make test, all tests passed locally

[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

[codecov[bot]]

Codecov Report

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

Project coverage is 100.00%. Comparing base (b4c9ccf) to head (19d993c). Report is 1 commits behind head on dev.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## dev #1994 +/- ## ========================================= Coverage 100.00% 100.00% ========================================= Files 188 188 Lines 11407 11407 Branches 1790 1790 ========================================= Hits 11407 11407 ```

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