refactor: use make_graphql_headers in pat_handler _test_pat_against_repo

[ebios-star]

Summary

Follow-up to merged #499, which introduced make_graphql_headers(token) in gittensor/utils/github_api_tools.py and replaced two inline {'Authorization': f'Bearer {token}', 'Content-Type': 'application/json'} dicts in execute_graphql_query and get_github_graphql_query.

gittensor/validator/pat_handler.py::_test_pat_against_repo still builds the same dict inline:

headers = {'Authorization': f'Bearer {pat}', 'Accept': 'application/json'}
try:
    response = requests.post(
        f'{BASE_GITHUB_API_URL}/graphql',
        json={'query': GRAPHQL_VIEWER_QUERY},
        headers=headers,
        timeout=GITHUB_HTTP_TIMEOUT_SECONDS,
    )

This is the one GraphQL Authorization: Bearer … header construction in the codebase that doesn't use make_graphql_headers. grep -rn "'Authorization': f'Bearer" confirms only this site and the helper's own definition remain.

Switching to make_graphql_headers(pat) puts every GraphQL Authorization header through one factory. The helper adds an explicit 'Content-Type': 'application/json' header — requests.post(..., json=...) already sets the same value automatically from the json= kwarg, so the wire request is unchanged.

Net: +2 / -2 lines, single file.

Type of Change

• Bug fix
• New feature
• Refactor
• Documentation
• Other

Testing

• pytest tests/ — all 1491 tests pass.

Checklist

• Code follows project style guidelines
• Self-review completed
• Changes are documented (if applicable)

[ebios-star]

@anderdc whenever you have a moment, this is a small follow-up to #499 that routes the one remaining inline GraphQL Authorization header construction through make_graphql_headers. Happy to revise scope if you'd prefer. Thanks!