elixir: 9.0.0 broke a public API for configuration that was "soft dep…

…recated" (#7930)

The documentation was never updated with the new configuration property and also I don't know if it was ever truly soft deprecated in the code. Easy to miss and I'm glad it's finally been hard deprecated.

src/platforms/elixir/index.mdx

@@ -42,7 +42,7 @@ config :sentry,
   dsn: "___PUBLIC_DSN___",
   environment_name: :prod,
   enable_source_code_context: true,
-  root_source_code_path: File.cwd!(),
+  root_source_code_paths: [File.cwd!()],
   tags: %{
     env: "production"
   },
@@ -197,12 +197,12 @@ defp aliases do
 end
 ```
 
-To enable, set `:enable_source_code_context` and `root_source_code_path`:
+To enable, set `:enable_source_code_context` and `root_source_code_paths`:
 
 ```elixir
 config :sentry,
   enable_source_code_context: true,
-  root_source_code_path: File.cwd!()
+  root_source_code_paths: [File.cwd!()]
 ```
 
 For more documentation, see [Sentry.Sources](https://hexdocs.pm/sentry/Sentry.Sources.html).