[geneva] Bump MessagePack version in test project to fix vulnerability warning

[CodeBlanch]

Following up on #2220 (comment)

Changes

• Bump MessagePack version in Geneva test project to fix vulnerability warning

Merge requirement checklist

• CONTRIBUTING guidelines followed (license requirements, nullable enabled, static analysis, etc.)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 58.95%. Comparing base (71655ce) to head (48ca948).
Report is 542 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #2227       +/-   ##
===========================================
- Coverage   73.91%   58.95%   -14.96%     
===========================================
  Files         267       45      -222     
  Lines        9615     3986     -5629     
===========================================
- Hits         7107     2350     -4757     
+ Misses       2508     1636      -872     

Flag	Coverage Δ
unittests-Exporter.Geneva	58.95% <ø> (?)

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see 248 files with indirect coverage changes