Fix unnecessary DAG file stats warning

[09Catho]

Fixes the repeated warning emitted when expected DAG relative paths are normalized for metrics tags.

The path is intentionally normalized, so DagFileInfo.normalized_file_path_for_stats now disables the invalid-character warning while preserving the normalized tag. A regression test covers both the normalized value and absence of a warning.

closes: #71084

Testing:

• standalone regression for normalization and suppressed warning
• python -m compileall -q airflow-core/src/airflow/dag_processing/manager.py airflow-core/tests/unit/dag_processing/test_manager.py
• git diff --check

The repository's uv run pytest ... and Ruff commands could not reach collection on Windows because pykerberos==1.2.4 requires the unavailable gssapi/gssapi.h header.

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• Yes (OpenAI Codex)

Generated-by: OpenAI Codex following the guidelines

[Copilot]

Pull request overview

This PR stops an expected, repeatedly-emitted stats-name warning when Dag file relative paths are normalized for metrics tags in the Dag processor. It keeps the normalized tag value while suppressing the invalid-character warning for this specific, intentionally-normalized path.

Changes:

• Disable warning emission when normalizing DagFileInfo.rel_path for stats tags by passing log_warning=False.
• Add a regression test asserting the normalized stats tag value and that no warning is emitted.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
airflow-core/src/airflow/dag_processing/manager.py	Suppresses normalization warning for Dag file path stats tag (log_warning=False) while preserving normalized output.
airflow-core/tests/unit/dag_processing/test_manager.py	Adds a regression test ensuring normalization happens and no warning is logged.

[ephraimbuddy]

closed in #71091 which came first. Thanks for the work!