chore(instrumentation-grpc): use local protobuf-ts plugin instead of buf.build remote

[overbalance]

Summary

• Use local @protobuf-ts/plugin instead of remote buf.build/community/timostamm-protobuf-ts plugin
• Remove unused buf.build/googleapis/googleapis dependency
• Prevents rate limiting issues and network dependency during builds

Test plan

• npm run protos:generate works offline

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.43%. Comparing base (0a1a631) to head (8bd2758).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6202      +/-   ##
==========================================
+ Coverage   95.41%   95.43%   +0.01%     
==========================================
  Files         317      317              
  Lines        9460     9521      +61     
  Branches     2199     2197       -2     
==========================================
+ Hits         9026     9086      +60     
- Misses        434      435       +1     

see 42 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.