chore: remove stale conformance runner comment

[FanouZeng-TT]

Description

integration_test_utils.py still contained a relative-path branch that claimed
FLAGS.test_data_dir was passed by run_conformance.sh:

if not Path(data_dir).is_absolute():
  # Actually, FLAGS.test_data_dir is passed by run_conformance.sh
  # Let's try to resolve it.
  pass

The repository has no run_conformance.sh, and the branch never resolved or
changed the path—the pass was followed by test_data.load(data_dir) with the
original value.

Fix: remove the obsolete no-op branch and pass FLAGS.test_data_dir directly
to the existing loader. Runtime behavior is unchanged.

Category (Required)

• Core Protocol: Changes to the base communication layer, global context, or breaking refactors. (Requires Technical Council approval)
• Governance/Contributing: Updates to GOVERNANCE.md, CONTRIBUTING.md, or CODEOWNERS. (Requires Governance Council approval)
• Capability: New schemas (Discovery, Cart, etc.) or extensions. (Requires Maintainer approval)
• Documentation: Updates to README, or documentations regarding schema or capabilities. (Requires Maintainer approval)
• Infrastructure: CI/CD, Linters, or build scripts. (Requires DevOps Maintainer approval)
• Maintenance: Version bumps, lockfile updates, or minor bug fixes. (Requires DevOps Maintainer approval)
• SDK: Language-specific SDK updates and releases. (Requires DevOps Maintainer approval)
• Samples / Conformance: Maintaining samples and the conformance suite. (Requires Maintainer approval)
• UCP Schema: Changes to the ucp-schema tool (resolver, linter, validator). (Requires Maintainer approval)
• Community Health (.github): Updates to templates, workflows, or org-level configs. (Requires DevOps Maintainer approval)

Related Issues

N/A

Checklist

• I have followed the Contributing Guide (including Conventional Commits title requirements and ! for breaking changes).
• I have updated the documentation (if applicable).
• My changes pass all local linting and formatting checks.
• I have added tests that prove my fix is effective or that my feature works.
• New and existing unit tests pass locally with my changes.
• (For Core/Capability) I have included/updated the relevant JSON schemas.
• I have regenerated Python Pydantic models by running generate_models.sh under python_sdk.

Screenshots / Logs (if applicable)

N/A — ruff check, ruff format --check, Python compilation, all repository pre-commit hooks, and git diff --check pass locally.