Remove spawn_blocking() call from GET /crates/:crate_id/:version/dependencies endpoint

[Turbo87]

because we can use diesel_async queries instead :)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.86%. Comparing base (fb906fc) to head (81d2332).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9869      +/-   ##
==========================================
- Coverage   88.86%   88.86%   -0.01%     
==========================================
  Files         289      289              
  Lines       30001    29994       -7     
==========================================
- Hits        26661    26653       -8     
- Misses       3340     3341       +1     

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