[infra] Fix post release steps related to artifacts output

[Kielek]

Fixes issues related to #6301
Failing build: https://github.com/open-telemetry/opentelemetry-dotnet/actions/runs/18153830423/job/51669380274

Changes

project.assets.json are located in different place

Merge requirement checklist

• CONTRIBUTING guidelines followed (license requirements, nullable enabled, static analysis, etc.)
• [ ] Unit tests added/updated
• [ ] Appropriate CHANGELOG.md files updated for non-trivial changes
• [ ] Changes in public API reviewed (if applicable)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.64%. Comparing base (0283361) to head (43dc8b6).
⚠️ Report is 1 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6549      +/-   ##
==========================================
- Coverage   86.70%   86.64%   -0.06%     
==========================================
  Files         258      258              
  Lines       11888    11888              
==========================================
- Hits        10307    10300       -7     
- Misses       1581     1588       +7     

Flag	Coverage Δ
unittests-Project-Experimental	86.59% <ø> (-0.09%)	⬇️
unittests-Project-Stable	86.37% <ø> (-0.28%)	⬇️
unittests-Solution	86.60% <ø> (+0.25%)	⬆️
unittests-UnstableCoreLibraries-Experimental	85.87% <ø> (+0.09%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.
see 3 files with indirect coverage changes

[github-actions]

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