controllers/krate/metadata: Remove spawn_blocking() usage

[Turbo87]

Best reviewed in "ignore whitespace changes" mode 😉

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.19%. Comparing base (a7d1ef4) to head (dc883e1).
Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #10004   +/-   ##
=======================================
  Coverage   89.18%   89.19%           
=======================================
  Files         295      295           
  Lines       30758    30768   +10     
=======================================
+ Hits        27433    27444   +11     
+ Misses       3325     3324    -1     

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