Turn off GitHub Pages for the .github repository

It seems that GitHub Pages is still activated for this repository, as I can visit the page <https://nbility-model.github.io/.github/>.

I think we can turn off GitHub Pages for this repository, because we do not need it. The documentation website, which does use GitHub Pages, is hosted in a [different repository](https://github.com/NBility-Model/nbility-model.github.io) anyway.