Remove unnecessary languages mapping in Tailwind for Ruby example (#40299)

The built-in Tailwind language already maps `HTML+ERB` to `erb`, and it
seems that `Ruby` files work as well just from enabling the language
server, so we can remove the unnecessary mapping.

Release Notes:
- N/A

docs/src/languages/ruby.md

@@ -260,10 +260,6 @@ In order to do that, you need to configure the language server so that it knows
   "lsp": {
     "tailwindcss-language-server": {
       "settings": {
-        "includeLanguages": {
-          "html+erb": "html",
-          "ruby": "html"
-        },
         "experimental": {
           "classRegex": ["\\bclass:\\s*['\"]([^'\"]*)['\"]"]
         }