Delete small-web-mode

[aadcg]

Implementing a proper Gemini and Gopher client takes plenty of effort and it seems to be better suited as a Nyxt extension. We have already demonstrated that the integrating this kind of functionality is possible. Interested parties should maintain and further develop it.

Inspiration could also be taken from tinmop.

Dropping the mode would also contribute to #3454.

[jmercouris]

I disagree with this one. I know that this would require a lot of effort to make them perfect, but they are pretty good as is, and I don't think they get in the way of anything.