Update validate-line-endings.py to not depend on pip packages

[Blue (OneBlue)]

Summary of the Pull Request

This change updates validate-line-endings.py to not have pip dependencies, which fail to install in the nightly & release pipelines.

PR Checklist

• Closes: Link to issue #xxx
• Communication: I've discussed this with core contributors already. If work hasn't been agreed, this work might be rejected
• Tests: Added/updated if needed and all pass
• Localization: All end user facing strings can be localized
• Dev docs: Added/updated if needed
• Documentation updated: If checked, please file a pull request on our docs repo and link it here: #xxx

Detailed Description of the Pull Request / Additional comments

Validation Steps Performed

[Copilot]

Pull request overview

This PR removes Python/pip package dependencies from the devops line-ending validation workflow so it can run in nightly/release pipelines without installing tools/devops/requirements.txt.

Changes:

• Replaced click + GitPython usage in validate-line-endings.py with argparse + git ls-files via subprocess.
• Removed the pip install -r tools/devops/requirements.txt step from the build-stage “Formatting & localization checks” job.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
tools/devops/validate-line-endings.py	Switches CLI + repo enumeration to stdlib + git CLI to eliminate pip dependencies.
.pipelines/build-stage.yml	Removes pip dependency installation step from the checks job to avoid pipeline failures.