chore(CODEOWNERS): remove blanket-ownership file (#1989)

The previous CODEOWNERS assigned every path in the repo to all three maintainers (@woile @Lee-W @noirbizarre), so every PR pinged all three for review regardless of scope. Recent commit history shows ownership in practice is much more concentrated and uneven, and the broad rule produces review-request spam without reflecting who actually maintains each area.

Removing the file lets GitHub fall back to repository-admin assignment without forcing a review request on three people for every change. A more granular per-area CODEOWNERS can be reintroduced later if maintainers want one.

Co-authored-by: Tim Hsiung <26526132+bearomorphism@users.noreply.github.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: bearomorphism