Update Thailand holidays: name change for October 13 holiday

[PPsyrius]

Proposed change

This PR adjusted the name for Thailand's October 13 holiday to "วันนวมินทรมหาราช" (HM King Bhumibol Adulyadej Memorial Day) as per new government announcement on September 26, 2023, as well as some test case simplification.

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/upgrade)
• 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

• I've followed the contributing guidelines
• I've added references to all holidays information sources used in this PR
• This PR is filed against beta branch of the repository
• This PR doesn't contain any merge conflicts and has clean commit history
• The code style looks good: make pre-commit command generates no changes
• All tests pass locally: make test, make tox (we strongly encourage adding tests to your code)
• The related documentation has been added/updated (check off the box for free if no updates is required)

[coveralls]

Pull Request Test Coverage Report for Build 6390092592

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 100.0%

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Totals
Change from base Build 6384409515:	0.0%
Covered Lines:	9541
Relevant Lines:	9541

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💛 - Coveralls

[KJhellico]

LGTM.

[arkid15r]

🇹🇭 LGTM