[docs] Fix website broken anchors

[wuchong]

Search before asking

• I searched in the issues and found nothing similar.

Description

https://github.com/apache/fluss/actions/runs/24150938424/job/70477440445?pr=2934

Warning:  Docusaurus found broken anchors!

Please check the pages of your site in the list below, and make sure you don't reference any anchor that does not exist.
Note: it's possible to ignore broken anchors with the 'onBrokenAnchors' Docusaurus configuration, and let the build pass.

Exhaustive list of all broken anchors found:
- Broken anchor on source page path = /docs/0.5/engine-flink/getting-started/:
   -> linking to /downloads/#fluss-connector
- Broken anchor on source page path = /docs/0.6/engine-flink/getting-started/:
   -> linking to /downloads/#fluss-connector
- Broken anchor on source page path = /docs/next/engine-flink/getting-started/:
   -> linking to /docs/next/engine-flink/ddl/#procedures
- Broken anchor on source page path = /docs/engine-flink/getting-started/:
   -> linking to /docs/engine-flink/ddl/#procedures

Willingness to contribute

• I'm willing to submit a PR!

[matrixsparse]

Hi @wuchong I'd like to take this. Could you assign me?