ref: Remove flag storage from StreamedSpan (1)

[sentrivana]

Description

Remove flags support from StreamedSpan for now. We will re-evaluate if we need this later.

Issues

Reminders

• Please add tests to validate your changes, and lint your code using tox -e linters.
• 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]

Semver Impact of This PR

🟢 Patch (bug fixes)

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[github-actions]

Codecov Results 📊

✅ 1707 passed | ⏭️ 184 skipped | Total: 1891 | Pass Rate: 90.27% | Execution Time: 2m 17s

All tests are passing successfully.

✅ Patch coverage is 100.00%. Project has 11869 uncovered lines.

Files with missing lines (1)

File	Patch %	Lines
traces.py	47.50%	⚠️ 42 Missing

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