Broken link to md_flexible example

[MakisH]

In the home page of AutoPAS, the link to the md-flexible example is broken: https://autopas.github.io/doxygen_documentation/git-master/examples/md-flexible

I would have fixed it already, but I don't really understand where this page draws its content from.

[FG-TUM]

It should be the front page of the oxygen documentation which is just the main README of the AutoPas repo. However, the commit tag on https://autopas.github.io/ is not the same as on github. There seems to be something not working with updating the whole documentation page through workflows. Needs investigation...