Bump next and @eventcatalog/core in /docs

Removes [next](https://github.com/vercel/next.js). It's no longer used after updating ancestor dependency [@eventcatalog/core](https://github.com/event-catalog/eventcatalog). These dependencies need to be updated together.


Removes `next`

Updates `@eventcatalog/core` from 0.6.8 to 2.17.3
- [Release notes](https://github.com/event-catalog/eventcatalog/releases)
- [Changelog](https://github.com/event-catalog/eventcatalog/blob/main/CHANGELOG.md)
- [Commits](https://github.com/event-catalog/eventcatalog/compare/@eventcatalog/core@0.6.8...v2.17.3)

---
updated-dependencies:
- dependency-name: next
  dependency-type: indirect
- dependency-name: "@eventcatalog/core"
  dependency-type: direct:production
...

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Author: dependabot[bot]