ref(openai-agents): Stop setting gen_ai.request.available_tools on Invoke Agent spans

[alexander-alderman-webb]

Description

The attribute is not well-defined for agents as an agent can make different tools available over the course of its execution.

See https://github.com/getsentry/rfcs/blob/main/text/0153-decoupling-sentrys-generative-ai-conventions-from-open-telemetry.md for details.

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 📊

✅ 99159 passed | ⏭️ 6757 skipped | Total: 105916 | Pass Rate: 93.62% | Execution Time: 358m 43s

📊 Comparison with Base Branch

Metric	Change
Total Tests	📈 +260
Passed Tests	📈 +281
Failed Tests	📉 -1
Skipped Tests	📉 -20

All tests are passing successfully.

✅ Patch coverage is 100.00%. Project has 2504 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          193       193         —
  Lines        24656     24719       +63
  Branches      8786      8830       +44
==========================================
+ Hits         22158     22215       +57
- Misses        2498      2504        +6
- Partials      1400      1415       +15

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