fix(otlp-transformer): pin protobufjs to 8.0.1

[pichlermarc]

Which problem is this PR solving?

Something is wrong with protobufjs@8.0.3 - when people install the @opentelemtry/otlp-transformer package today, they'll get this version and it's broken for bundlers (see bundler-tests on #6644)

This PR pins the version to 8.0.1 which is the last known good one.

Either merging this PR or both #6625 and #6629 fixes the issue, but this PR here should be quicker to get over the finish line.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.70%. Comparing base (cb38d7f) to head (972f7c7).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6646   +/-   ##
=======================================
  Coverage   95.70%   95.70%           
=======================================
  Files         375      375           
  Lines       12954    12954           
  Branches     3099     3099           
=======================================
  Hits        12398    12398           
  Misses        556      556           

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