Fix exists object storage logic

[lferran]

Description

Previous logic didn't work well for objects in gcs, as it was returning a 404 error response

How was this PR tested?

Describe how you tested this PR.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.22%. Comparing base (0ad193b) to head (61940a9).
Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2958      +/-   ##
==========================================
+ Coverage   84.01%   84.22%   +0.20%     
==========================================
  Files         487      487              
  Lines       35972    35976       +4     
  Branches    10966    10966              
==========================================
+ Hits        30222    30299      +77     
+ Misses       5224     5153      -71     
+ Partials      526      524       -2     

Flag	Coverage Δ
nidx	77.63% <ø> (+0.09%)	⬆️
nucliadb	76.04% <100.00%> (+0.24%)	⬆️
nucliadb-ingest	40.68% <0.00%> (+<0.01%)	⬆️
nucliadb-reader	42.05% <0.00%> (-0.02%)	⬇️
nucliadb-search	45.02% <0.00%> (+<0.01%)	⬆️
nucliadb-standalone	46.18% <0.00%> (+<0.01%)	⬆️
nucliadb-train	44.78% <0.00%> (+<0.01%)	⬆️
nucliadb-writer	46.84% <0.00%> (-0.03%)	⬇️
nucliadb_dataset	55.45% <ø> (ø)
nucliadb_models	84.27% <ø> (ø)
nucliadb_sdk	93.01% <ø> (ø)
nucliadb_telemetry	86.53% <ø> (ø)
nucliadb_utils	84.89% <100.00%> (+0.72%)	⬆️

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