fix: 連合なしアンケートのUpdateがリモートに配信されてしまうのを修正

[mei23]

What

連合なしアンケートに投票をするとUpdateがリモートに配信されてしまうのを修正

Why

Fix #11974

Additional info (optional)

ローカルのみ投稿が配信されなくなるのは確認

Checklist

• Read the contribution guide
• Test working in a local environment
• (If needed) Add story of storybook
• (If needed) Update CHANGELOG.md
• (If possible) Add tests

[codecov]

Codecov Report

All modified lines are covered by tests ✅

Comparison is base (e537497) 78.94% compared to head (fbdb843) 79.23%.
Report is 66 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop   #11977      +/-   ##
===========================================
+ Coverage    78.94%   79.23%   +0.28%     
===========================================
  Files          929      932       +3     
  Lines        99193    99700     +507     
  Branches      7883     8050     +167     
===========================================
+ Hits         78312    78999     +687     
+ Misses       20881    20701     -180     

Files	Coverage Δ
packages/backend/src/core/PollService.ts	56.36% <100.00%> (+0.80%)	⬆️

... and 82 files with indirect coverage changes

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[syuilo]

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