fix(worker): Avoid full index checkout on deletes

[nellh]

This prevents an expensive checkout during a file delete mutation that would often lead to timeouts of the operation and failed deletes.

[codecov]

Codecov Report

❌ Patch coverage is 89.28571% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 48.92%. Comparing base (ead8d93) to head (3b7fdde).

Files with missing lines	Patch %	Lines
services/datalad/datalad_service/tasks/files.py	92.59%	2 Missing ⚠️
packages/openneuro-server/src/datalad/dataset.ts	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4058      +/-   ##
==========================================
+ Coverage   48.89%   48.92%   +0.03%     
==========================================
  Files         686      686              
  Lines       38075    38102      +27     
  Branches     1897     1897              
==========================================
+ Hits        18616    18643      +27     
  Misses      19295    19295              
  Partials      164      164              

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[codecov]

Bundle Report

Bundle size has no change ✅