Remove unused sync fns

[Turbo87]

Now that we are using async database connections (almost) everywhere we can remove a lot of the code duplication that was introduced to enable the migration. At the same time we are dropping the async_ prefixes from these function, since they are not needed anymore and just clutter the code.

[codecov]

Codecov Report

Attention: Patch coverage is 77.67857% with 25 lines in your changes missing coverage. Please review.

Project coverage is 89.45%. Comparing base (c645ab9) to head (0d703b7).
Report is 7 commits behind head on main.

Files with missing lines	Patch %	Lines
src/bin/crates-admin/enqueue_job.rs	0.00%	16 Missing ⚠️
src/bin/crates-admin/delete_crate.rs	0.00%	3 Missing ⚠️
src/bin/crates-admin/yank_version.rs	0.00%	3 Missing ⚠️
src/bin/crates-admin/delete_version.rs	0.00%	2 Missing ⚠️
src/worker/jobs/archive_version_downloads.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #10048      +/-   ##
==========================================
+ Coverage   88.95%   89.45%   +0.49%     
==========================================
  Files         295      295              
  Lines       31454    31243     -211     
==========================================
- Hits        27980    27947      -33     
+ Misses       3474     3296     -178     

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