workers/jobs/dump_db: Remove unnecessary target_name field

[Turbo87]

We haven't used this in years and it makes it a bit more complicated to support other file types in the future.

Related:

• Data dumps feedback #2078

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 7 lines in your changes are missing coverage. Please review.

Project coverage is 88.48%. Comparing base (26c9e28) to head (e1affbb).
Report is 5 commits behind head on main.

Files	Patch %	Lines
src/worker/jobs/dump_db.rs	0.00%	5 Missing ⚠️
src/admin/enqueue_job.rs	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8719      +/-   ##
==========================================
+ Coverage   88.45%   88.48%   +0.02%     
==========================================
  Files         276      276              
  Lines       27449    27446       -3     
==========================================
+ Hits        24281    24285       +4     
+ Misses       3168     3161       -7     

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