ref(grpc): Use SegmentSource constants for streamed spans

[alexander-alderman-webb]

Description

Issues

Reminders

• Please add tests to validate your changes, and lint your code using uv run ruff.
• Add GH Issue ID & Linear ID (if applicable)
• PR title should use conventional commit style (feat:, fix:, ref:, meta:)
• For external contributors: CONTRIBUTING.md, Sentry SDK development docs, Discord community

[github-actions]

Codecov Results 📊

✅ 88726 passed | ⏭️ 6013 skipped | Total: 94739 | Pass Rate: 93.65% | Execution Time: 300m 21s

📊 Comparison with Base Branch

Metric	Change
Total Tests	—
Passed Tests	—
Failed Tests	—
Skipped Tests	—

✨ No test changes detected

All tests are passing successfully.

✅ Patch coverage is 100.00%. Project has 2367 uncovered lines.
✅ Project coverage is 89.87%. Comparing base (base) to head (head).

Coverage diff

@@            Coverage Diff             @@
##          main       #PR       +/-##
==========================================
+ Coverage    89.87%    89.87%        —%
==========================================
  Files          192       192         —
  Lines        23371     23373        +2
  Branches      8034      8034         —
==========================================
+ Hits         21004     21006        +2
- Misses        2367      2367         —
- Partials      1327      1327         —

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Generated by Codecov Action

[sentrivana]

Good catch!