Remove mobius-ai extra and dependency

[jambayk]

Describe your changes

The package mobius-ai doesn't exist on Pypi yet.

Checklist before requesting a review

• Add unit tests for this change.
• Make sure all tests can pass.
• Update documents if necessary.
• Lint and apply fixes to your code by running lintrunner -a
• Is this a user-facing change? If yes, give a description of this change to be included in the release notes.

(Optional) Issue link

[Copilot]

Pull request overview

This PR updates Olive’s package configuration to stop advertising/declaring the mobius-ai optional dependency as an installable extra, since the package is not available on PyPI. This primarily affects how olive-ai extras are generated (via setup.py reading olive/olive_config.json).

Changes:

• Removed the extra_dependencies requirement for the MobiusBuilder pass.
• Removed the mobius-ai extras entry from the package extra_dependencies map.