xml2rfc: migrate to python@3.14

[daeho-ro]

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[Copilot]

Pull Request Overview

This PR migrates the xml2rfc formula from Python 3.13 to Python 3.14 and updates several Python package dependencies.

• Migrates the formula to use python@3.14 instead of python@3.13
• Removes the certifi resource and adds its exclusion to the PyPI mappings
• Updates charset-normalizer and idna resources to newer versions

Reviewed Changes

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

File	Description
Formula/x/xml2rfc.rb	Updates Python version dependency and resource versions, removes certifi resource
pypi_formula_mappings.json	Adds xml2rfc configuration to exclude certifi package

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[github-actions]

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