docs: update error template.txt (#72263)
## Summary
Update [error
template.txt](https://github.com/vercel/next.js/blob/canary/errors/template.txt)
following #52038 changes.
## Description
1. Remove errorId header
2. Section header is double sharp `##` instead of four sharp `####`
### Adding or Updating Examples
- [x] The "examples guidelines" are followed from our contributing doc
https://github.com/vercel/next.js/blob/canary/contributing/examples/adding-examples.md
- [x] Make sure the linting passes by running `pnpm build && pnpm lint`.
See
https://github.com/vercel/next.js/blob/canary/contributing/repository/linting.md
Co-authored-by: Delba de Oliveira <32464864+delbaoliveira@users.noreply.github.com>
