Switch to Rails 7.1 defaults

In preparation for a Rails 7.2 upgrade

config/application.rb

@@ -9,7 +9,7 @@
 module Aggregator
   class Application < Rails::Application
     # Initialize configuration defaults for originally generated Rails version.
-    config.load_defaults 6.1
+    config.load_defaults 7.1
 
     # Please, add to the `ignore` list any other `lib` subdirectories that do
     # not contain `.rb` files, or that should not be reloaded or eager loaded.