Remove deprecated lsp-ruby package

[dmacvicar]

README from the github repo reads that the package is deprecated, as lsp-mode
supports ruby out of the box. The presence in the package list is confusing.

Brief summary of what the package does

# DEPRECATED

You do not need this package anymore! Just use `lsp-mode` directly. Read [the docs](https://github.com/emacs-lsp/lsp-mode/#configuration).

tl;dr:

Direct link to the package repository

https://github.com/emacs-lsp/lsp-ruby

Your association with the package

User

Relevant communications with the upstream package maintainer

//cc @gpittarelli

Checklist

N/A

[tarsius]

Also see #5894.