Update api_app.md to remove specific app name

Author: mveytsman

guides/source/api_app.md

@@ -450,7 +450,7 @@ built (like `config/application.rb`) and pass them to your preferred middleware,
 
 ```ruby
 # This also configures session_options for use below
-config.session_store :cookie_store, key: '_interslice_session'
+config.session_store :cookie_store, key: '_your_app_session'
 
 # Required for all session management (regardless of session_store)
 config.middleware.use ActionDispatch::Cookies