Improve docs around edge case for clojure-lsp classpath lookup failure

[bpringe]

I think the whole case deserves a mention in https://calva.io/quirks/ or in the troubleshooting section of this page https://calva.io/clojure-lsp/

Originally posted by @kurbatov in https://github.com/BetterThanTomorrow/calva/discussions/1194#discussioncomment-3450218