Consider deleting docs that aren't Celestia specific

[rootulp]

Context

While bumping Go version in https://github.com/celestiaorg/celestia-core/pull/1124, I noticed that pages in docs/* contain tutorials from CometBFT with Go versions.

Problem

Ideally we don't maintain those docs and consumers don't look at them in this repo b/c the source of truth for those docs exists upstream in CometBFT.

Proposal

Delete docs/* with the exception of docs/celestia-architecture. This may make it more difficult to pull upstream changes from CometBFT. I think we should prioritize ease of pulling upstream changes and maintainability. There isn't an obvious decision on whether deleting or keeping the docs is better on those criteria so I'm open to either deleting or keeping.