fix(lang/ruby): do not enable Rubocop as LSP if Solargraph is used (#4566)

## Description

Solargraph already delegates some diagnostics to Rubocop by itself if it
is installed on your system. However, if Rubocop is also enabled as an
LSP while you're using Solargraph, then all Rubocop diagnostics are
going to be duplicated and shown twice. Once from Solargraph after it
calls Rubocop, and again by Rubocop separately running as an LSP.

## Checklist

- [x] I've read the
[CONTRIBUTING](https://github.com/LazyVim/LazyVim/blob/main/CONTRIBUTING.md)
guidelines.

lua/lazyvim/plugins/extras/lang/ruby.lua

@@ -36,7 +36,10 @@ return {
           enabled = lsp == "solargraph",
         },
         rubocop = {
-          enabled = formatter == "rubocop",
+          -- If Solargraph and Rubocop are both enabled as an LSP,
+          -- diagnostics will be duplicated because Solargraph
+          -- already calls Rubocop if it is installed
+          enabled = formatter == "rubocop" and lsp ~= "solargraph",
         },
         standardrb = {
           enabled = formatter == "standardrb",