docs: Update language pages to indicate whether they are native or from an extension (#13827)

This PR updates the language pages in the docs to indicate whether the
support is available natively or provided by an extension.

Release Notes:

- N/A

docs/src/languages/elixir.md

@@ -1,7 +1,6 @@
 # Elixir
 
-- Tree Sitter: [tree-sitter-elixir](https://github.com/elixir-lang/tree-sitter-elixir)
-- Language Server: [elixir-ls](https://github.com/elixir-lsp/elixir-ls)
+Elixir support is available through the [Elixir extension](https://github.com/zed-industries/zed/tree/main/extensions/elixir).
 
 ## Choosing a language server