ref(openai-agents): Stop setting gen_ai.request.available_tools on Execute Tool spans

[alexander-alderman-webb]

Description

This doesn't make any sense. A tool execution doesn't have available tools.

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: 355m 23s

📊 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     24723       +67
  Branches      8786      8832       +46
==========================================
+ Hits         22158     22219       +61
- Misses        2498      2504        +6
- Partials      1400      1416       +16

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Generated by Codecov Action