5427e3c2de
Retire GitHub automation that is disabled, non-functional, unowned, or explicitly no longer wanted, together with its orphaned support code and tests. This removes the optional Dependabot version-update config; automatic team mentions and cc-review requests; last-successful and nightly branch advancement; reviewer pings; the disabled PR-comment bot; and the unused CI-resource upload path. Active CI, release, tvm-bot, and manual Docker-update workflows remain, with narrower permissions and event guards, plus refreshed issue-template and network-resource guidance. The behavior change is intentional: reviewer requests and team routing become manual, and the nightly and last-successful branches are no longer advanced by this repository. Dependabot security updates remain controlled by repository settings.