`index.md` Outdated, with dead links

[ztm0929]

docs/docs/index.md

Line 99 in 336c506

[<span class="underline">Beancount Source Code Documentation</span>](http://aumayr.github.io/beancount-docs-static/) (Dominik Aumayr): Sphinx-generated source code documentation of the Beancount codebase. The code to produce this is [<span class="underline">located here</span>](https://github.com/aumayr/beancount-docs).

These two links in the article seem to be outdated, and there is nothing relevant in the repository list of the target GitHub user (maybe he/she has removed them)

Obsolete links（404 error）:

• http://aumayr.github.io/beancount-docs-static/
• https://github.com/aumayr/beancount-docs

Affected pages:

https://beancount.github.io/docs/index.html