[stable4.5] Reset attendees participation on eventDrop

[backportbot-nextcloud]

Backport of #5532

[codecov]

Codecov Report

Attention: 4 lines in your changes are missing coverage. Please review.

Comparison is base (f470a11) 22.30% compared to head (d128edc) 22.30%.
Report is 1 commits behind head on stable4.5.

Additional details and impacted files

@@               Coverage Diff               @@
##             stable4.5    #5552      +/-   ##
===============================================
- Coverage        22.30%   22.30%   -0.01%     
  Complexity         388      388              
===============================================
  Files              240      240              
  Lines            11764    11769       +5     
  Branches          2294     2296       +2     
===============================================
+ Hits              2624     2625       +1     
- Misses            9140     9144       +4     

Flag	Coverage Δ
javascript	13.86% <20.00%> (+<0.01%)	⬆️
php	63.25% <ø> (ø)

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Files	Coverage Δ
src/fullcalendar/interaction/eventDrop.js	90.90% <20.00%> (-9.10%)	⬇️

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