Fix pprofile timestamp unix nano to be a fixed64

[dmathieu]

This was missed in my previous PR. The timestamp_unix_nano field has changed to be a fixed rather than uint.
See https://github.com/open-telemetry/opentelemetry-proto/blob/main/opentelemetry/proto/profiles/v1development/profiles.proto#L257

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.40%. Comparing base (32475fd) to head (352417f).
⚠️ Report is 6 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #13825      +/-   ##
==========================================
+ Coverage   91.39%   91.40%   +0.01%     
==========================================
  Files         647      646       -1     
  Lines       42597    42606       +9     
==========================================
+ Hits        38931    38944      +13     
+ Misses       2842     2839       -3     
+ Partials      824      823       -1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.