Update InternationalHolidays::_add_world_war_two_victory_day() method

[KJhellico]

Proposed change

Add Western (May 8) and Eastern (May 9) versions.

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)
• Bugfix (non-breaking change which fixes an issue)
• Breaking change (a code change causing existing functionality to break)
• New feature (new holidays functionality in general)

Checklist

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

[sonarqubecloud]

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]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (ce852f7) to head (c9faae3).
Report is 2 commits behind head on dev.

Additional details and impacted files

@@            Coverage Diff            @@
##               dev     #2064   +/-   ##
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  Coverage   100.00%   100.00%           
=========================================
  Files          191       191           
  Lines        11541     11543    +2     
  Branches      1742      1743    +1     
=========================================
+ Hits         11541     11543    +2     

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[PPsyrius]

This is probably the best compromise we could've come up with by having all of them shared the same holiday group entry - LGTM 🌐

[arkid15r]

👍