chore(mcp): Remove transaction-based tracing

[alexander-alderman-webb]

Description

I've also opened a PR to add parametrization to some tests on master: #7424

I've remove test_fastmcp_mixed_sync_async_tools() and test_fastmcp_multiple_tools(). The tests are no longer interesting now the outer transaction has been removed.

Issues

Closes #7101

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 📊

✅ 71575 passed | ❌ 1 failed | ⏭️ 3373 skipped | Total: 74949 | Pass Rate: 95.5% | Execution Time: 222m 54s

📊 Comparison with Base Branch

Metric	Change
Total Tests	📉 -64087
Passed Tests	📉 -60330
Failed Tests	📈 +1
Skipped Tests	📉 -3758

➕ New Tests (1)

View new tests

• test_headers[no headers]
  • File: tests.integrations.aws_lambda.test_aws_lambda
  • Status: ❌ Failing

❌ Failed Tests

test_headers[no headers]

File: tests.integrations.aws_lambda.test_aws_lambda
Suite: py3.13-aws_lambda
Error: ValueError: too many values to unpack (expected 1)

Stack Trace

tests/integrations/aws_lambda/test_aws_lambda.py:624: in test_headers
    (error_event,) = envelopes
    ^^^^^^^^^^^^^^
E   ValueError: too many values to unpack (expected 1)

✅ Patch coverage is 88.36%. Project has 2260 uncovered lines.
❌ Project coverage is 90.11%. Comparing base (8a17bc6) to head (b4b9d89).

Files with missing lines (1)

File	Patch %	Lines
sentry_sdk/integrations/mcp.py	88.36%	⚠️ 22 Missing and 31 partials

Coverage diff

@@            Coverage Diff             @@
##        master       #PR       +/-##
==========================================
- Coverage    90.20%    90.11%    -0.09%
==========================================
  Files          193       185        -8
  Lines        25788     22861     -2927
  Branches      9530      8342     -1188
==========================================
+ Hits         23261     20601     -2660
- Misses        2527      2260      -267
- Partials      1432      1343       -89

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