project, contestの終了時期を未定に戻す更新が出来るようにした

[Tennessine699]

resolves #694

[codecov]

Codecov Report

Attention: Patch coverage is 92.00000% with 2 lines in your changes missing coverage. Please review.

Project coverage is 72.85%. Comparing base (c50236b) to head (822d70e).

Files with missing lines	Patch %	Lines
internal/infrastructure/repository/project_impl.go	87.50%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #727      +/-   ##
==========================================
+ Coverage   72.59%   72.85%   +0.25%     
==========================================
  Files          42       42              
  Lines        3843     3857      +14     
==========================================
+ Hits         2790     2810      +20     
+ Misses        902      889      -13     
- Partials      151      158       +7     

Flag	Coverage Δ
integration	72.85% <92.00%> (+0.25%)	⬆️
unit	72.85% <92.00%> (+0.25%)	⬆️

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