[Exporter.Geneva] Fix test dependency conflict

[vishweshbankwar]

Fixes build failures from #1888. Use pre-release versions consistently for all packages.

ref: https://github.com/open-telemetry/opentelemetry-dotnet-contrib/actions/runs/9521755414/job/26249939293?pr=1888

Changes

Please provide a brief description of the changes here.

For significant contributions please make sure you have completed the following items:

• Appropriate CHANGELOG.md updated for non-trivial changes
• Design discussion issue #
• Changes in public API reviewed

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 65.19%. Comparing base (71655ce) to head (879b474).
Report is 307 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1889      +/-   ##
==========================================
- Coverage   73.91%   65.19%   -8.73%     
==========================================
  Files         267       35     -232     
  Lines        9615     3660    -5955     
==========================================
- Hits         7107     2386    -4721     
+ Misses       2508     1274    -1234     

Flag	Coverage Δ
unittests-Exporter.Geneva	65.19% <ø> (?)

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see 249 files with indirect coverage changes

[CodeBlanch]

LGTM