Show accurate message when clojure-lsp fails to download

[bpringe]

I noticed when the clojure-lsp nightly build download was failing. An error would be logged in the developer console but a popup info message would show that an older version was downloaded. We should show an error popup explaining that the download failed instead.

[Extension Host] Error downloading clojure-lsp. Error: Not Found

Nightly was attempted to be downloaded, the download failed, and this message popped up.