ICM fixes (3/n)

[Hariharan Seshadri (hariharans29)]

Description

Fix ICM issue: https://portal.microsofticm.com/imp/v5/incidents/details/31000000567822/summary

The ICM is mainly about 2 issues in validate_package.py which was fixed by #27840.
But the ICM also references another issue in whisper_jump_times.py which is what this PR fixes

Motivation and Context

ICM fixes

[Copilot]

Pull request overview

This PR addresses an additional security-related ICM item in the Whisper tooling by removing a shell-based command execution path in whisper_jump_times.py, aligning it with the safer approach taken in the earlier validate_package.py fix.

Changes:

• Replace os.system("pip install ninja") with subprocess.run([...], check=True) to avoid shell invocation.
• Invoke pip via sys.executable -m pip for a more reliable interpreter/environment match.

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[Tianlei Wu (tianleiwu)]

No findings from my review. Switching the fallback from os.system("pip install ninja") to subprocess.run([sys.executable, "-m", "pip", "install", "ninja"], check=True) removes shell invocation, uses the active interpreter consistently, and makes installation failures explicit.