Delete CODEOWNERS file to eliminate reviewer notification overload

The CODEOWNERS file was causing excessive notifications by automatically
requesting reviews from entire teams on every PR. Since we have no branch
protection rules enforcing CODEOWNERS approval, this file only served to
spam team members without providing actual merge protection.

Going forward:
- Reviews will be triaged through manual review requests and notifications
- Team members with write access can still merge as before
- This eliminates automatic review requests while maintaining the same
  security posture (no enforcement was in place anyway)

This significantly reduces notification fatigue for the python-sdk team
(6 members) and python-sdk-auth team (2 members) who were being auto-assigned
to every relevant PR.

Reported-by: User

Author: felixweinberger