chore: cleanup unused workflows (#81391)
Cleans up unused workflows & scripts
- bankrupt workflow is superseded by the [stale
workflow](https://github.com/vercel/next.js/blob/canary/.github/workflows/issue_stale.yml)
- filtering issues by version hasn't been used in 9 months and can be
accomplished with a GH search
- the AI triaging tool has largely been more noise than signal. the
existing alerts that have been surfaced in the triage channel have been
sufficient
